U.S. patent number 11,456,790 [Application Number 16/991,808] was granted by the patent office on 2022-09-27 for multi-beam selection for beamformed multiple input multiple output wireless communications.
This patent grant is currently assigned to QUALCOMM Incorporated. The grantee listed for this patent is QUALCOMM Incorporated. Invention is credited to Tianyang Bai, Tao Luo, Wooseok Nam, Sungwoo Park, Kiran Venugopal.
United States Patent |
11,456,790 |
Park , et al. |
September 27, 2022 |
Multi-beam selection for beamformed multiple input multiple output
wireless communications
Abstract
Methods, systems, and devices for wireless communications are
described for multiple-input multiple-output (MIMO) millimeter wave
(mmW) communications of two or more MIMO streams via two or more
beams. A sequential technique may be used for configuring MIMO
communications, in which analog RF beamforming parameters are
determined based on reference signal measurements during a beam
sweeping procedure. Then, digital baseband beamforming parameters
may be determined and used for baseband processing of two or more
MIMO streams. The digital baseband beamforming parameters may
include baseband precoding parameters used for transmitting the two
or more MIMO streams on the two or more beams, and baseband
combiner parameters used for receiving the two or more MIMO streams
on the two or more beams.
Inventors: |
Park; Sungwoo (San Diego,
CA), Venugopal; Kiran (Raritan, NJ), Bai; Tianyang
(Somerville, NJ), Nam; Wooseok (San Diego, CA), Luo;
Tao (San Diego, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Assignee: |
QUALCOMM Incorporated (San
Diego, CA)
|
Family
ID: |
1000006586572 |
Appl.
No.: |
16/991,808 |
Filed: |
August 12, 2020 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20210050893 A1 |
Feb 18, 2021 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62888391 |
Aug 16, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B
7/0639 (20130101); H04B 7/0695 (20130101); H04B
7/0626 (20130101); H04B 7/0417 (20130101); H04B
7/0617 (20130101); H04L 5/0048 (20130101) |
Current International
Class: |
H04B
7/02 (20180101); H04B 7/06 (20060101); H04B
7/0417 (20170101); H04L 5/00 (20060101) |
Field of
Search: |
;375/267 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Partial International Search
Report--PCT/US2020/046144--ISA/EPO--dated Oct. 22, 2020. cited by
applicant .
International Search Report and Written
Opinion--PCT/US2020/046144--ISA/EPO--dated Jan. 25, 2021. cited by
applicant.
|
Primary Examiner: Kassa; Zewdu A
Attorney, Agent or Firm: Holland & Hart LLP
Parent Case Text
CROSS REFERENCE
The present application for patent claims the benefit of U.S.
Provisional Patent Application No. 62/888,391 by PARK et al.,
entitled "MULTI-BEAM SELECTION FOR BEAMFORMED MULTIPLE INPUT
MULTIPLE OUTPUT WIRELESS COMMUNICATIONS," filed Aug. 16, 2019,
assigned to the assignee hereof, and expressly incorporated by
reference herein.
Claims
What is claimed is:
1. An apparatus for wireless communication, comprising: a
processor, memory coupled with the processor; and instructions
stored in the memory and executable by the processor to cause the
apparatus to: transmit, from a first wireless device, a plurality
of reference signals to a second wireless device using a plurality
of combinations of analog beamforming parameters associated with
two or more beams that are configured to carry two or more
multiple-input multiple-output streams, wherein the plurality of
reference signals are transmitted for different combinations of one
or more sets of transmit beamforming parameters and one or more
sets of receive beamforming parameters; receive, from the second
wireless device, a report that indicates a first combination of
analog beamforming parameters is selected for the analog
beamforming parameters at the second wireless device; and
communicate with the second wireless device via the two or more
beams based at least in part on the first combination of analog
beamforming parameters.
2. The apparatus of claim 1, wherein the instructions are further
executable to cause the apparatus to: receive, from the second
wireless device, a second reference signal that is transmitted
using the first combination of analog beamforming parameters;
estimate an effective channel between the first wireless device and
the second wireless device based on one or more measurements of the
second reference signal; and determine a set of transmission
baseband precoder parameters to be applied to baseband signals of
the two or more beams based at least in part on the estimating the
effective channel.
3. The apparatus of claim 2, wherein communications with the second
wireless device include data communications via the two or more
multiple-input multiple-output streams on the two or more beams,
wherein the two or more beams use the first combination of analog
beamforming parameters and the set of transmission baseband
precoder parameters, and wherein the data communications include a
third reference signal for measurement at the second wireless
device and determination of a set of receive baseband combiner
parameters to be applied to baseband signals of the two or more
beams at the second wireless device.
4. The apparatus of claim 1, wherein the report that indicates the
first combination of analog beamforming parameters provides a
codebook index value for a codebook of beamforming parameters, and
wherein the codebook of beamforming parameters maps codebook index
values to the different combinations of the one or more sets of
transmit beamforming parameters and the one or more sets of receive
beamforming parameters.
5. The apparatus of claim 1, wherein the first combination of
analog beamforming parameters is associated with a first reference
signal transmission that has a highest mutual information (MI)
value of the plurality of reference signals.
6. The apparatus of claim 1, wherein the first wireless device is a
base station and the second wireless device is a user equipment
(UE), wherein the plurality of reference signals are downlink
reference signals transmitted to the UE in a beam sweeping
procedure, and wherein the downlink reference signals include one
or more of a channel state information reference signal (CSI-RS),
one or more reference signals transmitted in a synchronization
signal block (SSB), or any combinations thereof.
7. The apparatus of claim 1, wherein the first wireless device is a
user equipment (UE) and the second wireless device is a base
station, and wherein the plurality of reference signals are uplink
reference signals transmitted to the base station in a beam
sweeping procedure, and wherein the uplink reference signals
include sounding reference signals (SRS).
8. The apparatus of claim 1, wherein the plurality of reference
signals include reference signals that are specific to
transmissions from the first wireless device to the second wireless
device, and wherein the first wireless device determines a second
combination of analog beamforming parameters for use at the first
wireless device based on one or more different reference signals
that are specific to transmissions from the second wireless device
to the first wireless device.
9. The apparatus of claim 1, wherein the first wireless device
determines a set of transmission baseband precoder parameters to be
applied to baseband signals for transmissions using the two or more
beams based at least in part on a second reference signal received
from the second wireless device, wherein the baseband precoder
parameters are used to transform input from the two or more
multiple-input multiple-output streams into baseband streams of a
plurality of radio frequency transmit chains, and wherein the first
combination of analog beamforming parameters are used to transform
the baseband streams of the plurality of radio frequency transmit
chains into wideband waveforms that are provided to a plurality of
antennas.
10. The apparatus of claim 1, wherein the instructions are further
executable to cause the apparatus to: receive an indication from
the second wireless device of a set of transmission baseband
precoder parameters to be applied to baseband signals for
transmissions from the first wireless device using the two or more
beams, and wherein the indication from the second wireless device
is a precoding matrix indicator (PMI) that is mapped to a codebook
of sets of transmission baseband precoder parameters.
11. The apparatus of claim 1, wherein the instructions are further
executable to cause the apparatus to: transmit a data transmission
and a third reference signal to the second wireless device via the
two or more multiple-input multiple-output streams on the two or
more beams, wherein the second wireless device determines a set of
receive baseband combiner parameters to be applied to baseband
signals of received transmissions using the two or more beams based
at least in part on the third reference signal, and wherein the
third reference signal is a demodulation reference signal
(DMRS).
12. An apparatus for wireless communication, comprising: a
processor, memory coupled with the processor; and instructions
stored in the memory and executable by the processor to cause the
apparatus to: measure, at a second wireless device, a channel
quality of a plurality of reference signals that are transmitted by
a first wireless device using a plurality of combinations of analog
beamforming parameters for two or more beams that carry two or more
multiple-input multiple-output streams, wherein the plurality of
reference signals are transmitted for different combinations of one
or more sets of transmit beamforming parameters and one or more
sets of receive beamforming parameters; select a first combination
of analog beamforming parameters based at least in part on the
measured channel quality of the plurality of reference signals; and
communicate with the first wireless device via the two or more
beams based at least in part on the first combination of analog
beamforming parameters.
13. The apparatus of claim 12, wherein the instructions are further
executable to cause the apparatus to: estimate an effective channel
between the second wireless device and the first wireless device
for each of the different combinations of the one or more sets of
transmit beamforming parameters and the one or more sets of receive
beamforming parameters, and wherein the first combination of analog
beamforming parameters is selected based on a magnitude of the
effective channel estimates.
14. The apparatus of claim 12, wherein the instructions are further
executable to cause the apparatus to: transmit a second reference
signal to the first wireless device using the first combination of
analog beamforming parameters for determination of a set of
transmission baseband precoder parameters at the first wireless
device, wherein communications with the first wireless device
include data communications via the two or more multiple-input
multiple-output streams on the two or more beams, and wherein the
two or more beams use the first combination of analog beamforming
parameters and the set of transmission baseband precoder
parameters.
15. The apparatus of claim 12, wherein the instructions are further
executable to cause the apparatus to: transmit a report that
indicates the first combination of analog beamforming parameters is
selected for the analog beamforming parameters, and wherein the
report indicates a codebook index value for a codebook of
beamforming parameters, and wherein the codebook of beamforming
parameters maps codebook index values to the different combinations
of the one or more sets of transmit beamforming parameters and the
one or more sets of receive beamforming parameters.
16. The apparatus of claim 12, wherein the first wireless device is
a base station and the second wireless device is a user equipment
(UE), wherein the plurality of reference signals are downlink
reference signals transmitted to the UE in a beam sweeping
procedure, and wherein the downlink reference signals include one
or more of a channel state information reference signal (CSI-RS),
one or more reference signals transmitted in a synchronization
signal block (SSB), or any combinations thereof.
17. The apparatus of claim 12, wherein the first wireless device is
a user equipment (UE) and the second wireless device is a base
station, wherein the plurality of reference signals are uplink
reference signals transmitted to the base station in a beam
sweeping procedure, and wherein the uplink reference signals
include sounding reference signals (SRS).
18. The apparatus of claim 12, wherein the instructions are further
executable to cause the apparatus to: determine a set of
transmission baseband precoder parameters to be applied to baseband
signals for transmissions from the second wireless device using the
two or more beams based at least in part on the plurality of
reference signals transmitted by the first wireless device.
19. The apparatus of claim 12, wherein the instructions are further
executable to cause the apparatus to: transmit a second reference
signal to the first wireless device using the first combination of
analog beamforming parameters for determination of a set of
transmission baseband precoder parameters to be applied to baseband
signals for transmissions from the first wireless device using the
two or more beams.
20. The apparatus of claim 12, wherein the instructions are further
executable to cause the apparatus to: transmit an indication to the
first wireless device of a set of transmission baseband precoder
parameters to be applied to baseband signals for transmissions from
the first wireless device using the two or more beams, wherein the
indication to the first wireless device is a precoding matrix
indicator (PMI) that is mapped to a codebook of sets of
transmission baseband precoder parameters.
21. The apparatus of claim 12, wherein the instructions are further
executable to cause the apparatus to: receive a data transmission
and a third reference signal from the first wireless device via the
two or more multiple-input multiple-output streams on the two or
more beams, wherein the third reference signal is a demodulation
reference signal (DMRS); determine, based at least in part on
measurements of the third reference signal, a set of receive
baseband combiner parameters to be applied to baseband signals of
received transmissions using the two or more beams; estimate an
effective channel between the second wireless device and the first
wireless device based on measurements of the third reference
signal; determine the set of receive baseband combiner parameters
based on the estimating; and decode the data transmission using the
receive baseband combiner parameters.
22. An apparatus for wireless communication, comprising: a
processor, memory coupled with the processor; and instructions
stored in the memory and executable by the processor to cause the
apparatus to: receive, at a first wireless device, a plurality of
reference signals that are transmitted by a second wireless device
using a plurality of combinations of analog beamforming parameters
for two or more beams that carry two or more multiple-input
multiple-output streams; determine a set of analog beamforming
parameters for the two or more beams based at least in part on
measurements of the plurality of reference signals; determine a set
of transmission baseband precoder parameters to be applied to
baseband signals of the two or more beams based at least in part on
a channel estimation of a channel between the first wireless device
and the second wireless device; determine a set of receive baseband
combiner parameters to be applied to baseband signals of the two or
more beams based at least in part on the channel estimation; and
communicate with the second wireless device using the two or more
beams based at least in part on the set of analog beamforming
parameters, the set of transmission baseband precoder parameters,
and the set of receive baseband combiner parameters.
23. The apparatus of claim 22, wherein: the analog beamforming
parameters are used to transform signals received at a plurality of
antennas to baseband signals that are provided to a plurality of
radio frequency receive chains; and the baseband combiner
parameters are used to transform an output of the plurality of
radio frequency receive chains into the two or more multiple-input
multiple-output streams.
24. The apparatus of claim 22, wherein: the baseband precoder
parameters are used to transform the two or more multiple-input
multiple-output streams into baseband signals that are provided to
a plurality of radio frequency transmit chains; and the analog
beamforming parameters are used to transform the baseband signals
received at the radio frequency transmit chains into radio
frequency signals for transmission from a plurality of
antennas.
25. A method for wireless communication, comprising: transmitting,
from a first wireless device, a plurality of reference signals to a
second wireless device using a plurality of combinations of analog
beamforming parameters associated with two or more beams that are
configured to carry two or more multiple-input multiple-output
streams, wherein the plurality of reference signals are transmitted
for different combinations of one or more sets of transmit
beamforming parameters and one or more sets of receive beamforming
parameters; receiving, from the second wireless device, a report
that indicates a first combination of analog beamforming parameters
is selected for the analog beamforming parameters at the second
wireless device; and communicating with the second wireless device
via the two or more beams based at least in part on the first
combination of analog beamforming parameters.
26. The method of claim 25, further comprising: receiving, from the
second wireless device, a second reference signal that is
transmitted using the first combination of analog beamforming
parameters; estimating an effective channel between the first
wireless device and the second wireless device based on one or more
measurements of the second reference signal; and determining a set
of transmission baseband precoder parameters to be applied to
baseband signals of the two or more beams based at least in part on
the estimating the effective channel.
27. The method of claim 25, wherein the report that indicates the
first combination of analog beamforming parameters provides a
codebook index value for a codebook of beamforming parameters, and
wherein the codebook of beamforming parameters maps codebook index
values to the different combinations of the one or more sets of
transmit beamforming parameters and the one or more sets of receive
beamforming parameters.
28. The method of claim 25, wherein the first wireless device is a
base station and the second wireless device is a user equipment
(UE), wherein the plurality of reference signals are downlink
reference signals transmitted to the UE in a beam sweeping
procedure, and wherein the downlink reference signals include one
or more of a channel state information reference signal (CSI-RS),
one or more reference signals transmitted in a synchronization
signal block (SSB), or any combinations thereof.
29. The method of claim 25, wherein the first wireless device is a
user equipment (UE) and the second wireless device is a base
station, wherein the plurality of reference signals are uplink
reference signals transmitted to the base station in a beam
sweeping procedure, and wherein the uplink reference signals
include sounding reference signals (SRS).
30. The method of claim 25, further comprising: receiving an
indication from the second wireless device of a set of transmission
baseband precoder parameters to be applied to baseband signals for
transmissions from the first wireless device using the two or more
beams, wherein the indication from the second wireless device is a
precoding matrix indicator (PMI) that is mapped to a codebook of
sets of transmission baseband precoder parameters.
Description
FIELD OF TECHNOLOGY
The following relates generally to wireless communications and more
specifically to multi-beam selection for beamformed multiple input
multiple output wireless communications.
BACKGROUND
Wireless communications systems are widely deployed to provide
various types of communication content such as voice, video, packet
data, messaging, broadcast, and so on. These systems may be capable
of supporting communication with multiple users by sharing the
available system resources (for example, time, frequency, and
power). Examples of such multiple-access systems include fourth
generation (4G) systems such as Long Term Evolution (LTE) systems,
LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth
generation (5G) systems which may be referred to as New Radio (NR)
systems. These systems may employ technologies such as code
division multiple access (CDMA), time division multiple access
(TDMA), frequency division multiple access (FDMA), orthogonal
frequency division multiple access (OFDMA), or discrete Fourier
transform spread orthogonal frequency division multiplexing
(DFT-S-OFDM).
A wireless multiple-access communications system may include a
number of base stations or network access nodes, each
simultaneously supporting communication for multiple communication
devices, each of which may be otherwise known as a user equipment
(UE). Some wireless communications systems may support beamforming
operations for directional communications. Beamforming, which may
also be referred to as spatial filtering, directional transmission,
or directional reception, may be a signal processing technique that
may be used at a transmitting device or a receiving device to
select, shape, or steer an antenna beam (for example, a transmit
directional beam, a receive directional beam) along a spatial path
between the transmitting device and the receiving device. Some
wireless communications systems may support beamforming operations
to mitigate pathloss and blockages with respect to the spatial
path. As demand for communication efficiency increases, it may be
desirable for a wireless communications system to target low
latencies and improve reliability for beamforming operations.
SUMMARY
The described techniques may relate to configuring a communication
device, which may be a user equipment (UE), a base station, or
both, to support multiple-input multiple-output (MIMO) millimeter
wave (mmW) communications (also referred to as directional
communications). In some examples, the described techniques may be
used to configure the communication device for MIMO communications
with one or more other devices using two or more beams. In some
cases, a sequential technique may be used for configuring MIMO
communications, in which analog RF beamforming parameters (e.g.,
analog beamforming parameters for a number of frequency sub-bands)
are determined based on reference signal measurements during a beam
sweeping procedure in which a number of combinations of analog RF
beamforming parameters for two or more beams are transmitted. Then,
digital baseband beamforming parameters (e.g., digital beamforming
parameters for baseband signals that are not modulated on a carrier
frequency) may be determined and used for baseband processing of
two or more MIMO streams. The digital baseband beamforming
parameters may include baseband precoding parameters used for
transmitting the two or more MIMO streams on the two or more beams,
and baseband combiner parameters used for receiving the two or more
MIMO streams on the two or more beams.
The described techniques may be used to configure communication
devices to perform a beamforming operation, such as a beam
selection operation, a beam training operation, or the like, and
may configure the communication device with a codebook to improve
beamforming reliability and data rate for MIMO mmW
communications.
A method of wireless communication is described. The method may
include transmitting, from a first wireless device, a set of
reference signals to a second wireless device using a set of
combinations of analog beamforming parameters associated with two
or more beams that are configured to carry two or more
multiple-input multiple-output streams, where the set of reference
signals are transmitted for different combinations of one or more
sets of transmit beamforming parameters and one or more sets of
receive beamforming parameters, receiving, from the second wireless
device, a report that indicates a first combination of analog
beamforming parameters is selected for the analog beamforming
parameters at the second wireless device, and communicating with
the second wireless device via the two or more beams based on the
first combination of analog beamforming parameters.
An apparatus for wireless communication is described. The apparatus
may include a processor, memory coupled with the processor, and
instructions stored in the memory. The instructions may be
executable by the processor to cause the apparatus to transmit,
from a first wireless device, a set of reference signals to a
second wireless device using a set of combinations of analog
beamforming parameters associated with two or more beams that are
configured to carry two or more multiple-input multiple-output
streams, where the set of reference signals are transmitted for
different combinations of one or more sets of transmit beamforming
parameters and one or more sets of receive beamforming parameters,
receive, from the second wireless device, a report that indicates a
first combination of analog beamforming parameters is selected for
the analog beamforming parameters at the second wireless device,
and communicate with the second wireless device via the two or more
beams based on the first combination of analog beamforming
parameters.
Another apparatus for wireless communication is described. The
apparatus may include means for transmitting, from a first wireless
device, a set of reference signals to a second wireless device
using a set of combinations of analog beamforming parameters
associated with two or more beams that are configured to carry two
or more multiple-input multiple-output streams, where the set of
reference signals are transmitted for different combinations of one
or more sets of transmit beamforming parameters and one or more
sets of receive beamforming parameters, receiving, from the second
wireless device, a report that indicates a first combination of
analog beamforming parameters is selected for the analog
beamforming parameters at the second wireless device, and
communicating with the second wireless device via the two or more
beams based on the first combination of analog beamforming
parameters.
A non-transitory computer-readable medium storing code for wireless
communication is described. The code may include instructions
executable by a processor to transmit, from a first wireless
device, a set of reference signals to a second wireless device
using a set of combinations of analog beamforming parameters
associated with two or more beams that are configured to carry two
or more multiple-input multiple-output streams, where the set of
reference signals are transmitted for different combinations of one
or more sets of transmit beamforming parameters and one or more
sets of receive beamforming parameters, receive, from the second
wireless device, a report that indicates a first combination of
analog beamforming parameters is selected for the analog
beamforming parameters at the second wireless device, and
communicate with the second wireless device via the two or more
beams based on the first combination of analog beamforming
parameters.
Some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein may further include
operations, features, means, or instructions for receiving, from
the second wireless device, a second reference signal that may be
transmitted using the first combination of analog beamforming
parameters, estimating an effective channel between the first
wireless device and the second wireless device based on one or more
measurements of the second reference signal, and determining a set
of transmission baseband precoder parameters to be applied to
baseband signals of the two or more beams based on the estimating
the effective channel.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the communicating with
the second wireless device includes data communications via the two
or more multiple-input multiple-output streams on the two or more
beams, where the two or more beams use the first combination of
analog beamforming parameters and the set of transmission baseband
precoder parameters. In some examples of the method, apparatuses,
and non-transitory computer-readable medium described herein, the
data communications include a third reference signal for
measurement at the second wireless device and determination of a
set of receive baseband combiner parameters to be applied to
baseband signals of the two or more beams at the second wireless
device.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the report that
indicates the first combination of analog beamforming parameters
provides a codebook index value for a codebook of beamforming
parameters, and where the codebook of beamforming parameters maps
codebook index values to the different combinations of the one or
more sets of transmit beamforming parameters and the one or more
sets of receive beamforming parameters.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the first combination of
analog beamforming parameters may be associated with a first
reference signal transmission that may have a highest mutual
information (MI) value of the set of reference signals.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the first wireless
device may be a base station and the second wireless device may be
a UE, and where the set of reference signals may be downlink
reference signals transmitted to the UE in a beam sweeping
procedure. In some examples of the method, apparatuses, and
non-transitory computer-readable medium described herein, the
downlink reference signals include one or more of a channel state
information reference signal (CSI-RS), one or more reference
signals transmitted in a synchronization signal block (SSB), or any
combinations thereof.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the first wireless
device may be a UE and the second wireless device may be a base
station, and where the set of reference signals may be uplink
reference signals transmitted to the base station in a beam
sweeping procedure. In some examples of the method, apparatuses,
and non-transitory computer-readable medium described herein, the
uplink reference signals include sounding reference signals
(SRS).
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the set of reference
signals include reference signals that are specific to
transmissions from the first wireless device to the second wireless
device, and where the first wireless device determines a second
combination of analog beamforming parameters for use at the first
wireless device based on one or more different reference signals
that may be specific to transmissions from the second wireless
device to the first wireless device.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the first wireless
device determines a set of transmission baseband precoder
parameters to be applied to baseband signals for transmissions
using the two or more beams based on a second reference signal
received from the second wireless device, where the baseband
precoder parameters may be used to transform input from the two or
more multiple-input multiple-output streams into baseband streams
of a set of radio frequency transmit chains, and where the first
combination of analog beamforming parameters are used to transform
the baseband streams of the set of radio frequency transmit chains
into wideband waveforms that are provided to a set of antennas.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the second wireless
device determines a set of transmission baseband precoder
parameters to be applied to baseband signals for transmissions from
the second wireless device using the two or more beams based on the
set of reference signals transmitted by the first wireless
device.
Some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein may further include
operations, features, means, or instructions for receiving an
indication from the second wireless device of a set of transmission
baseband precoder parameters to be applied to baseband signals for
transmissions from the first wireless device using the two or more
beams. In some examples of the method, apparatuses, and
non-transitory computer-readable medium described herein, the
indication from the second wireless device may be a precoding
matrix indicator (PMI) that is mapped to a codebook of sets of
transmission baseband precoder parameters.
Some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein may further include
operations, features, means, or instructions for transmitting a
data transmission and a third reference signal to the second
wireless device via the two or more multiple-input multiple-output
streams on the two or more beams, and where the second wireless
device determines a set of receive baseband combiner parameters to
be applied to baseband signals of received transmissions using the
two or more beams based on the third reference signal. In some
examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the third reference
signal may be a demodulation reference signal (DMRS).
A method of wireless communication is described. The method may
include measuring, at a second wireless device, a channel quality
of a set of reference signals that are transmitted by a first
wireless device using a set of combinations of analog beamforming
parameters for two or more beams that carry two or more
multiple-input multiple-output streams, where the set of reference
signals are transmitted for different combinations of one or more
sets of transmit beamforming parameters and one or more sets of
receive beamforming parameters, selecting a first combination of
analog beamforming parameters based on the measured channel quality
of the set of reference signals, and communicating with the first
wireless device via the two or more beams based on the first
combination of analog beamforming parameters.
An apparatus for wireless communication is described. The apparatus
may include a processor, memory coupled with the processor, and
instructions stored in the memory. The instructions may be
executable by the processor to cause the apparatus to measure, at a
second wireless device, a channel quality of a set of reference
signals that are transmitted by a first wireless device using a set
of combinations of analog beamforming parameters for two or more
beams that carry two or more multiple-input multiple-output
streams, where the set of reference signals are transmitted for
different combinations of one or more sets of transmit beamforming
parameters and one or more sets of receive beamforming parameters,
select a first combination of analog beamforming parameters based
on the measured channel quality of the set of reference signals,
and communicate with the first wireless device via the two or more
beams based on the first combination of analog beamforming
parameters.
Another apparatus for wireless communication is described. The
apparatus may include means for measuring, at a second wireless
device, a channel quality of a set of reference signals that are
transmitted by a first wireless device using a set of combinations
of analog beamforming parameters for two or more beams that carry
two or more multiple-input multiple-output streams, where the set
of reference signals are transmitted for different combinations of
one or more sets of transmit beamforming parameters and one or more
sets of receive beamforming parameters, selecting a first
combination of analog beamforming parameters based on the measured
channel quality of the set of reference signals, and communicating
with the first wireless device via the two or more beams based on
the first combination of analog beamforming parameters.
A non-transitory computer-readable medium storing code for wireless
communication is described. The code may include instructions
executable by a processor to measure, at a second wireless device,
a channel quality of a set of reference signals that are
transmitted by a first wireless device using a set of combinations
of analog beamforming parameters for two or more beams that carry
two or more multiple-input multiple-output streams, where the set
of reference signals are transmitted for different combinations of
one or more sets of transmit beamforming parameters and one or more
sets of receive beamforming parameters, select a first combination
of analog beamforming parameters based on the measured channel
quality of the set of reference signals, and communicate with the
first wireless device via the two or more beams based on the first
combination of analog beamforming parameters.
Some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein may further include
operations, features, means, or instructions for estimating an
effective channel between the second wireless device and the first
wireless device for each of the different combinations of the one
or more sets of transmit beamforming parameters and the one or more
sets of receive beamforming parameters, and where the first
combination of analog beamforming parameters may be selected based
on a magnitude of the effective channel estimates.
Some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein may further include
operations, features, means, or instructions for transmitting a
second reference signal to the first wireless device using the
first combination of analog beamforming parameters for
determination of a set of transmission baseband precoder parameters
at the first wireless device. In some examples of the method,
apparatuses, and non-transitory computer-readable medium described
herein, the communicating with the first wireless device includes
data communications via the two or more multiple-input
multiple-output streams on the two or more beams, where the two or
more beams use the first combination of analog beamforming
parameters and the set of transmission baseband precoder
parameters.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the data communications
include a third reference signal for determination of a set of
receive baseband combiner parameters to be applied to baseband
signals of the two or more beams at the second wireless device.
Some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein may further include
operations, features, means, or instructions for transmitting a
report that indicates the first combination of analog beamforming
parameters are selected for the analog beamforming parameters, and
where the report indicates a codebook index value for a codebook of
beamforming parameters, and where the codebook of beamforming
parameters maps codebook index values to the different combinations
of the one or more sets of transmit beamforming parameters and the
one or more sets of receive beamforming parameters.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the first combination of
analog beamforming parameters may be associated with a first
reference signal transmission that may have a highest mutual
information (MI) value of the set of reference signals.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the first wireless
device may be a base station and the second wireless device may be
a UE, and where the set of reference signals may be downlink
reference signals transmitted to the UE in a beam sweeping
procedure. In some examples of the method, apparatuses, and
non-transitory computer-readable medium described herein, the
downlink reference signals include one or more of a channel state
information reference signal (CSI-RS), one or more reference
signals transmitted in a synchronization signal block (SSB), or any
combinations thereof.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the first wireless
device may be a UE and the second wireless device may be a base
station, and where the set of reference signals may be uplink
reference signals transmitted to the base station in a beam
sweeping procedure. In some examples of the method, apparatuses,
and non-transitory computer-readable medium described herein, the
uplink reference signals include sounding reference signals
(SRS).
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the set of reference
signals include reference signals that are specific to
transmissions from the second wireless device to the first wireless
device, and where the second wireless device determines a second
combination of analog beamforming parameters for use at the second
wireless device based on one or more different reference signals
that are specific to transmissions from the second wireless device
to the first wireless device.
Some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein may further include
operations, features, means, or instructions for determining a set
of transmission baseband precoder parameters to be applied to
baseband signals for transmissions from the second wireless device
using the two or more beams based on the set of reference signals
transmitted by the first wireless device.
Some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein may further include
operations, features, means, or instructions for transmitting a
second reference signal to the first wireless device using the
first combination of analog beamforming parameters for
determination of a set of transmission baseband precoder parameters
to be applied to baseband signals for transmissions from the first
wireless device using the two or more beams.
Some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein may further include
operations, features, means, or instructions for transmitting an
indication to the first wireless device of a set of transmission
baseband precoder parameters to be applied to baseband signals for
transmissions from the first wireless device using the two or more
beams. In some examples of the method, apparatuses, and
non-transitory computer-readable medium described herein, the
indication to the first wireless device may be a precoding matrix
indicator (PMI) that is mapped to a codebook of sets of
transmission baseband precoder parameters.
Some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein may further include
operations, features, means, or instructions for receiving a data
transmission and a third reference signal from the first wireless
device via the two or more multiple-input multiple-output streams
on the two or more beams, and determining, based on measurements of
the third reference signal, a set of receive baseband combiner
parameters to be applied to baseband signals of received
transmissions using the two or more beams. In some examples of the
method, apparatuses, and non-transitory computer-readable medium
described herein, the third reference signal may be a demodulation
reference signal (DMRS).
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the determining the set
of received baseband combiner parameters may include operations,
features, means, or instructions for estimating an effective
channel between the second wireless device and the first wireless
device based on measurements of the third reference signal, and
determining the set of receive baseband combiner parameters based
on the estimating. Some examples of the method, apparatuses, and
non-transitory computer-readable medium described herein may
further include operations, features, means, or instructions for
decoding the data transmission using the receive baseband combiner
parameters.
A method of wireless communication is described. The method may
include receiving, at a first wireless device, a set of reference
signals that are transmitted by a second wireless device using a
set of combinations of analog beamforming parameters for two or
more beams that carry two or more multiple-input multiple-output
streams, determining a set of analog beamforming parameters for the
two or more beams based on measurements of the set of reference
signals, determining a set of transmission baseband precoder
parameters to be applied to baseband signals of the two or more
beams based on a channel estimation of a channel between the first
wireless device and the second wireless device, determining a set
of receive baseband combiner parameters to be applied to baseband
signals of the two or more beams based on the channel estimation,
and communicating with the second wireless device using the two or
more beams based on the set of analog beamforming parameters, the
set of transmission baseband precoder parameters, and the set of
receive baseband combiner parameters.
An apparatus for wireless communication is described. The apparatus
may include a processor, memory coupled with the processor, and
instructions stored in the memory. The instructions may be
executable by the processor to cause the apparatus to receive, at a
first wireless device, a set of reference signals that are
transmitted by a second wireless device using a set of combinations
of analog beamforming parameters for two or more beams that carry
two or more multiple-input multiple-output streams, determine a set
of analog beamforming parameters for the two or more beams based on
measurements of the set of reference signals, determine a set of
transmission baseband precoder parameters to be applied to baseband
signals of the two or more beams based on a channel estimation of a
channel between the first wireless device and the second wireless
device, determine a set of receive baseband combiner parameters to
be applied to baseband signals of the two or more beams based on
the channel estimation, and communicate with the second wireless
device using the two or more beams based on the set of analog
beamforming parameters, the set of transmission baseband precoder
parameters, and the set of receive baseband combiner
parameters.
Another apparatus for wireless communication is described. The
apparatus may include means for receiving, at a first wireless
device, a set of reference signals that are transmitted by a second
wireless device using a set of combinations of analog beamforming
parameters for two or more beams that carry two or more
multiple-input multiple-output streams, determining a set of analog
beamforming parameters for the two or more beams based on
measurements of the set of reference signals, determining a set of
transmission baseband precoder parameters to be applied to baseband
signals of the two or more beams based on a channel estimation of a
channel between the first wireless device and the second wireless
device, determining a set of receive baseband combiner parameters
to be applied to baseband signals of the two or more beams based on
the channel estimation, and communicating with the second wireless
device using the two or more beams based on the set of analog
beamforming parameters, the set of transmission baseband precoder
parameters, and the set of receive baseband combiner
parameters.
A non-transitory computer-readable medium storing code for wireless
communication is described. The code may include instructions
executable by a processor to receive, at a first wireless device, a
set of reference signals that are transmitted by a second wireless
device using a set of combinations of analog beamforming parameters
for two or more beams that carry two or more multiple-input
multiple-output streams, determine a set of analog beamforming
parameters for the two or more beams based on measurements of the
set of reference signals, determine a set of transmission baseband
precoder parameters to be applied to baseband signals of the two or
more beams based on a channel estimation of a channel between the
first wireless device and the second wireless device, determine a
set of receive baseband combiner parameters to be applied to
baseband signals of the two or more beams based on the channel
estimation, and communicate with the second wireless device using
the two or more beams based on the set of analog beamforming
parameters, the set of transmission baseband precoder parameters,
and the set of receive baseband combiner parameters.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the analog beamforming
parameters may be used to transform signals received at a set of
antennas to baseband signals that may be provided to a set of radio
frequency receive chains, and the baseband combiner parameters may
be used to transform an output of the set of radio frequency
receive chains into the two or more multiple-input multiple-output
streams.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the baseband precoder
parameters may be used to transform the two or more multiple-input
multiple-output streams into baseband signals that may be provided
to a set of radio frequency transmit chains, and the analog
beamforming parameters may be used to transform the baseband
signals received at the radio frequency transmit chains into radio
frequency signals for transmission from a set of antennas.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the first wireless
device may be a UE and the second wireless device may be a base
station, and where the set of reference signals may be downlink
reference signals transmitted to the UE in a beam sweeping
procedure. In some examples of the method, apparatuses, and
non-transitory computer-readable medium described herein, the
downlink reference signals include one or more of a channel state
information reference signal (CSI-RS), one or more reference
signals transmitted in a synchronization signal block (SSB), or any
combinations thereof.
In some examples of the method, apparatuses, and non-transitory
computer-readable medium described herein, the first wireless
device may be a base station and the second wireless device may be
a UE, and where the set of reference signals may be uplink
reference signals transmitted to the base station in a beam
sweeping procedure. In some examples of the method, apparatuses,
and non-transitory computer-readable medium described herein, the
uplink reference signals include sounding reference signals
(SRS).
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 through 5 illustrate examples of wireless communications
systems that support multi-beam selection for beamformed MIMO
wireless communications in accordance with aspects of the present
disclosure.
FIGS. 6 through 11 illustrate example of process flows that support
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure.
FIGS. 12 and 13 show block diagrams of devices that support
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure.
FIG. 14 shows a block diagram of a communications manager that
supports multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure.
FIG. 15 shows a diagram of a system including a user equipment (UE)
that supports multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure.
FIG. 16 shows a diagram of a system including a base station that
supports multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure.
FIGS. 17 through 25 show flowcharts illustrating methods that
support multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure.
DETAILED DESCRIPTION
Some wireless communication systems may include communication
devices, such as user equipment (UEs) and base stations, for
example, next-generation NodeBs or giga-NodeBs (which may be
referred to as gNBs), that may support multiple radio access
technologies. Examples of radio access technologies include 4G
systems such as Long Term Evolution (LTE) systems and fifth
generation (5G) systems which may be referred to as New Radio (NR)
systems. Some wireless communications systems, such as
multiple-input multiple output (MIMO) systems, may configure the
communication devices to support millimeter wave (mmW)
communications (also referred to as directional communications). In
some examples, the communication devices may experience one or more
of a pathloss or a blockage with respect to a spatial path for the
mmW communications. As a result, the communication devices may
support beamforming operations to counter one or more of the
pathloss or the blockage, among other examples.
According to various aspects of the present disclosure, techniques
are provided for configuring a communication device (which may be
referred to herein interchangeably as a wireless device), which may
be a UE or a base station (or any other wireless communication
device), to support MIMO mmW communications of two or more MIMO
streams via two or more beams. In some cases, a sequential
technique may be used for configuring MIMO communications, in which
analog RF beamforming parameters (e.g., analog beamforming
parameters for a number of frequency sub-bands) are determined
based on reference signal measurements during a beam sweeping
procedure in which a number of combinations of analog RF
beamforming parameters for two or more beams are transmitted. Then,
digital baseband beamforming parameters (e.g., digital beamforming
parameters for baseband signals that are not modulated on a carrier
frequency) may be determined and used for baseband processing of
two or more MIMO streams. The digital baseband beamforming
parameters may include baseband precoding parameters used for
transmitting the two or more MIMO streams on the two or more beams,
and baseband combiner parameters used for receiving the two or more
MIMO streams on the two or more beams.
The communication devices may, for example, perform a beamforming
operation in accordance with one or more codebooks to improve
beamforming reliability and data rate for mmW communications. The
codebooks may have a number N possible beamforming vectors. In some
examples, N may be dependent on N.sub.T and N.sub.R, where N.sub.T
refers to a number of physical transmit antennas and N.sub.R refers
to a number of physical receive antennas. In some examples, to
enable multi-stream operation (e.g., in MIMO systems), the
communications devices may determine and select multiple transmit
directional beams and receive directional beams. The multiple
transmit directional beams and receive directional beams may be
used simultaneously at the communication devices (e.g., at a
transmitting device, at a receiving device). Additionally, in some
examples, the various directional beams may be from a same or
different panel of the communication devices. For example, the
communication devices may include multiple panels, each panel may
include an array of same or different antennas (e.g., one or more
of N.sub.T or N.sub.R).
In some examples, the communication devices may perform a search
over a number of possible pairs of beamforming vectors (f.sub.n,
w.sub.m). As demand for communication efficiency increases, it may
be desirable for the communications devices to target low latencies
and improve reliability for beamforming operations, and more
specifically to determine and select multiple beamforming pairs
(f.sub.n, w.sub.m) to improve data rates in MIMO systems. In some
examples, the communication devices may be configured with one or
more signaling mechanisms to iteratively select beam weight for
maximizing MIMO rate, in accordance with one or more analog
codebook constraints at the communication devices.
Particular aspects of the subject matter described in this
disclosure may be implemented to realize one or more of the
following potential advantages. The techniques employed by the
described communication devices may provide benefits and
enhancements to the operation of the communication devices. For
example, operations performed by the described communication
devices may provide improvements to power consumption when
performing beam operations. In some examples, configuring the
described communication devices to perform sequential determination
of beamforming parameters for multi-beam selection with
uplink-downlink beam training may support improvements to spectral
efficiency, higher data rates and, in some examples, may promote
high reliability and low latency for beamforming operations, among
other benefits.
Aspects of the disclosure are initially described in the context of
several exemplary wireless communications systems. Aspects of the
disclosure are further illustrated by and described with reference
to process flows that relate to sequential determination of
beamforming parameters with uplink-downlink beam training. Aspects
of the disclosure are further illustrated by and described with
reference to apparatus diagrams, system diagrams, and flowcharts
that relate to multi-beam selection for beamformed MIMO wireless
communications.
FIG. 1 illustrates an example of a wireless communications system
100 that supports multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure. The wireless communications system 100 includes base
stations 105, UEs 115, and a core network 130. In some examples,
the wireless communications system 100 may be a Long Term Evolution
(LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro
network, or a New Radio (NR) network. In some cases, wireless
communications system 100 may support enhanced broadband
communications, ultra-reliable (e.g., mission critical)
communications, low latency communications, or communications with
low-cost and low-complexity devices.
Base stations 105 may wirelessly communicate with UEs 115 via one
or more base station antennas. Base stations 105 described herein
may include or may be referred to by those skilled in the art as a
base transceiver station, a radio base station, an access point, a
radio transceiver, a NodeB, an eNodeB (eNB), a next-generation
NodeB or giga-NodeB (either of which may be referred to as a gNB),
a Home NodeB, a Home eNodeB, or some other suitable terminology.
Wireless communications system 100 may include base stations 105 of
different types (e.g., macro or small cell base stations). The UEs
115 described herein may be able to communicate with various types
of base stations 105 and network equipment including macro eNBs,
small cell eNBs, gNBs, relay base stations, and the like.
Each base station 105 may be associated with a particular
geographic coverage area 110 in which communications with various
UEs 115 is supported. Each base station 105 may provide
communication coverage for a respective geographic coverage area
110 via communication links 125, and communication links 125
between a base station 105 and a UE 115 may utilize one or more
carriers. Communication links 125 shown in wireless communications
system 100 may include uplink transmissions from a UE 115 to a base
station 105, or downlink transmissions from a base station 105 to a
UE 115. Downlink transmissions may also be called forward link
transmissions while uplink transmissions may also be called reverse
link transmissions.
The geographic coverage area 110 for a base station 105 may be
divided into sectors making up a portion of the geographic coverage
area 110, and each sector may be associated with a cell. For
example, each base station 105 may provide communication coverage
for a macro cell, a small cell, a hot spot, or other types of
cells, or various combinations thereof. In some examples, a base
station 105 may be movable and therefore provide communication
coverage for a moving geographic coverage area 110. In some
examples, different geographic coverage areas 110 associated with
different technologies may overlap, and overlapping geographic
coverage areas 110 associated with different technologies may be
supported by the same base station 105 or by different base
stations 105. The wireless communications system 100 may include,
for example, a heterogeneous LTE/LTE-A/LTE-A Pro or NR network in
which different types of base stations 105 provide coverage for
various geographic coverage areas 110.
The term "cell" refers to a logical communication entity used for
communication with a base station 105 (e.g., over a carrier), and
may be associated with an identifier for distinguishing neighboring
cells (e.g., a physical cell identifier (PCID), a virtual cell
identifier (VCID)) operating via the same or a different carrier.
In some examples, a carrier may support multiple cells, and
different cells may be configured according to different protocol
types (e.g., machine-type communication (MTC), narrowband
Internet-of-Things (NB-IoT), enhanced mobile broadband (eMBB), or
others) that may provide access for different types of devices. In
some cases, the term "cell" may refer to a portion of a geographic
coverage area 110 (e.g., a sector) over which the logical entity
operates.
UEs 115 may be dispersed throughout the wireless communications
system 100, and each UE 115 may be stationary or mobile. A UE 115
may also be referred to as a mobile device, a wireless device, a
remote device, a handheld device, or a subscriber device, or some
other suitable terminology, where the "device" may also be referred
to as a unit, a station, a terminal, or a client. A UE 115 may also
be a personal electronic device such as a cellular phone, a
personal digital assistant (PDA), a tablet computer, a laptop
computer, or a personal computer. In some examples, a UE 115 may
also refer to a wireless local loop (WLL) station, an Internet of
Things (IoT) device, an Internet of Everything (IoE) device, or an
MTC device, or the like, which may be implemented in various
articles such as appliances, vehicles, meters, or the like.
Some UEs 115, such as MTC or IoT devices, may be low cost or low
complexity devices, and may provide for automated communication
between machines (e.g., via Machine-to-Machine (M2M)
communication). M2M communication or MTC may refer to data
communication technologies that allow devices to communicate with
one another or a base station 105 without human intervention. In
some examples, M2M communication or MTC may include communications
from devices that integrate sensors or meters to measure or capture
information and relay that information to a central server or
application program that can make use of the information or present
the information to humans interacting with the program or
application. Some UEs 115 may be designed to collect information or
enable automated behavior of machines. Examples of applications for
MTC devices include smart metering, inventory monitoring, water
level monitoring, equipment monitoring, healthcare monitoring,
wildlife monitoring, weather and geological event monitoring, fleet
management and tracking, remote security sensing, physical access
control, and transaction-based business charging.
Some UEs 115 may be configured to employ operating modes that
reduce power consumption, such as half-duplex communications (e.g.,
a mode that supports one-way communication via transmission or
reception, but not transmission and reception simultaneously). In
some examples half-duplex communications may be performed at a
reduced peak rate. Other power conservation techniques for UEs 115
include entering a power saving "deep sleep" mode when not engaging
in active communications, or operating over a limited bandwidth
(e.g., according to narrowband communications). In some cases, UEs
115 may be designed to support critical functions (e.g., mission
critical functions), and a wireless communications system 100 may
be configured to provide ultra-reliable communications for these
functions.
In some cases, a UE 115 may also be able to communicate directly
with other UEs 115 (e.g., using a peer-to-peer (P2P) or
device-to-device (D2D) protocol). One or more of a group of UEs 115
utilizing D2D communications 135 may be within the geographic
coverage area 110 of a base station 105. Other UEs 115 in such a
group may be outside the geographic coverage area 110 of a base
station 105, or be otherwise unable to receive transmissions from a
base station 105. In some cases, groups of UEs 115 communicating
via D2D communications 135 may utilize a one-to-many (1:M) system
in which each UE 115 transmits to every other UE 115 in the group.
In some cases, a base station 105 facilitates the scheduling of
resources for D2D communications 135. In other cases, D2D
communications 135 are carried out between UEs 115 without the
involvement of a base station 105.
Base stations 105 may communicate with the core network 130 and
with one another. For example, base stations 105 may interface with
the core network 130 through backhaul links 120 (e.g., via an S1,
N2, N3, or other interface). Base stations 105 may communicate with
one another over backhaul links 120 (e.g., via an X2, Xn, or other
interface) either directly (e.g., directly between base stations
105) or indirectly (e.g., via core network 130).
The core network 130 may provide user authentication, access
authorization, tracking, Internet Protocol (IP) connectivity, and
other access, routing, or mobility functions. The core network 130
may be an evolved packet core (EPC), which may include at least one
mobility management entity (MME), at least one serving gateway
(S-GW), and at least one Packet Data Network (PDN) gateway (P-GW).
The MME may manage non-access stratum (e.g., control plane)
functions such as mobility, authentication, and bearer management
for UEs 115 served by base stations 105 associated with the EPC.
User IP packets may be transferred through the S-GW, which itself
may be connected to the P-GW. The P-GW may provide IP address
allocation as well as other functions. The P-GW may be connected to
the network operators IP services. The operators IP services may
include access to the Internet, Intranet(s), an IP Multimedia
Subsystem (IMS), or a Packet-Switched (PS) Streaming Service
150.
At least some of the network devices, such as a base station 105,
may include subcomponents such as an access network entity 140,
which may be an example of an access node controller (ANC). Each
access network entity 140 may communicate with UEs 115 through a
number of other access network transmission entities, which may be
referred to as a radio head, a smart radio head, or a
transmission/reception point (TRP) 145. In some configurations,
various functions of each access network entity or base station 105
may be distributed across various network devices (e.g., radio
heads and access network controllers) or consolidated into a single
network device (e.g., a base station 105).
Wireless communications system 100 may operate using one or more
frequency bands, typically in the range of 300 megahertz (MHz) to
300 gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is
known as the ultra-high frequency (UHF) region or decimeter band,
since the wavelengths range from approximately one decimeter to one
meter in length. UHF waves may be blocked or redirected by
buildings and environmental features. However, the waves may
penetrate structures sufficiently for a macro cell to provide
service to UEs 115 located indoors. Transmission of UHF waves may
be associated with smaller antennas and shorter range (e.g., less
than 100 km) compared to transmission using the smaller frequencies
and longer waves of the high frequency (HF) or very high frequency
(VHF) portion of the spectrum below 300 MHz.
Wireless communications system 100 may also operate in a super high
frequency (SHF) region using frequency bands from 3 GHz to 30 GHz,
also known as the centimeter band. The SHF region includes bands
such as the 5 GHz industrial, scientific, and medical (ISM) bands,
which may be used opportunistically by devices that may be capable
of tolerating interference from other users.
Wireless communications system 100 may also operate in an extremely
high frequency (EHF) region of the spectrum (e.g., from 30 GHz to
300 GHz), also known as the millimeter band. In some examples,
wireless communications system 100 may support millimeter wave
(mmW) communications between UEs 115 and base stations 105, and EHF
antennas of the respective devices may be even smaller and more
closely spaced than UHF antennas. In some cases, this may
facilitate use of antenna arrays within a UE 115. However, the
propagation of EHF transmissions may be subject to even greater
atmospheric attenuation and shorter range than SHF or UHF
transmissions. Techniques disclosed herein may be employed across
transmissions that use one or more different frequency regions, and
designated use of bands across these frequency regions may differ
by country or regulating body.
In some cases, wireless communications system 100 may utilize both
licensed and unlicensed radio frequency spectrum bands. For
example, wireless communications system 100 may employ License
Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access
technology, or NR technology in an unlicensed band such as the 5
GHz ISM band. When operating in unlicensed radio frequency spectrum
bands, wireless devices such as base stations 105 and UEs 115 may
employ listen-before-talk (LBT) procedures to ensure a frequency
channel is clear before transmitting data. In some cases,
operations in unlicensed bands may be based on a carrier
aggregation configuration in conjunction with component carriers
operating in a licensed band (e.g., LAA). Operations in unlicensed
spectrum may include downlink transmissions, uplink transmissions,
peer-to-peer transmissions, or a combination of these. Duplexing in
unlicensed spectrum may be based on frequency division duplexing
(FDD), time division duplexing (TDD), or a combination of both.
In some examples, base station 105 or UE 115 may be equipped with
multiple antennas, which may be used to employ techniques such as
transmit diversity, receive diversity, MIMO communications, or
beamforming. For example, wireless communications system 100 may
use a transmission scheme between a transmitting device (e.g., a
base station 105) and a receiving device (e.g., a UE 115), where
the transmitting device is equipped with multiple antennas and the
receiving device is equipped with one or more antennas. MIMO
communications may employ multipath signal propagation to increase
the spectral efficiency by transmitting or receiving multiple
signals via different spatial layers, which may be referred to as
spatial multiplexing. The multiple signals may, for example, be
transmitted by the transmitting device via different antennas or
different combinations of antennas. Likewise, the multiple signals
may be received by the receiving device via different antennas or
different combinations of antennas. Each of the multiple signals
may be referred to as a separate spatial stream, and may carry bits
associated with the same data stream (e.g., the same codeword) or
different data streams. Different spatial layers may be associated
with different antenna ports used for channel measurement and
reporting. MIMO techniques include single-user MIMO (SU-MIMO) where
multiple spatial layers are transmitted to the same receiving
device, and multiple-user MIMO (MU-MIMO) where multiple spatial
layers are transmitted to multiple devices.
As discussed herein, beamforming, which may also be referred to as
spatial filtering, directional transmission, or directional
reception, is a signal processing technique that may be used at a
transmitting device or a receiving device (e.g., a base station 105
or a UE 115) to shape or steer one or more antenna beams (e.g.,
transmit beam(s) or receive beam(s)) along a spatial path between
the transmitting device and the receiving device. Beamforming may
be achieved by combining the signals communicated via antenna
elements of an antenna array such that signals propagating at
particular orientations with respect to an antenna array experience
constructive interference while others experience destructive
interference. The adjustment of signals communicated via the
antenna elements may include a transmitting device or a receiving
device applying certain amplitude and phase offsets to signals
carried via each of the antenna elements associated with the
device. The adjustments associated with each of the antenna
elements may be defined by a beamforming weight set associated with
a particular orientation (e.g., with respect to the antenna array
of the transmitting device or receiving device, or with respect to
some other orientation).
In some cases, the antennas of a base station 105 or UE 115 may be
located within one or more antenna arrays, which may support MIMO
operations, or transmit or receive beamforming. For example, one or
more base station antennas or antenna arrays may be co-located at
an antenna assembly, such as an antenna tower. In some cases,
antennas or antenna arrays associated with a base station 105 may
be located in diverse geographic locations. A base station 105 may
have an antenna array with a number of rows and columns of antenna
ports that the base station 105 may use to support beamforming of
communications with a UE 115. Likewise, a UE 115 may have one or
more antenna arrays that may support various MIMO or beamforming
operations.
In some cases, wireless communications system 100 may be a
packet-based network that operate according to a layered protocol
stack. In the user plane, communications at the bearer or Packet
Data Convergence Protocol (PDCP) layer may be IP-based. A Radio
Link Control (RLC) layer may perform packet segmentation and
reassembly to communicate over logical channels. A Medium Access
Control (MAC) layer may perform priority handling and multiplexing
of logical channels into transport channels. The MAC layer may also
use hybrid automatic repeat request (HARQ) to provide
retransmission at the MAC layer to improve link efficiency. In the
control plane, the Radio Resource Control (RRC) protocol layer may
provide establishment, configuration, and maintenance of an RRC
connection between a UE 115 and a base station 105 or core network
130 supporting radio bearers for user plane data. At the Physical
layer, transport channels may be mapped to physical channels.
In some cases, UEs 115 and base stations 105 may support
retransmissions of data to increase the likelihood that data is
received successfully. HARQ feedback is one technique of increasing
the likelihood that data is received correctly over a communication
link 125. HARQ may include a combination of error detection (e.g.,
using a cyclic redundancy check (CRC)), forward error correction
(FEC), and retransmission (e.g., automatic repeat request (ARQ)).
HARQ may improve throughput at the MAC layer in poor radio
conditions (e.g., signal-to-noise conditions). In some cases, a
wireless device may support same-slot HARQ feedback, where the
device may provide HARQ feedback in a specific slot for data
received in a previous symbol in the slot. In other cases, the
device may provide HARQ feedback in a subsequent slot, or according
to some other time interval.
Time intervals in LTE or NR may be expressed in multiples of a
basic time unit, which may, for example, refer to a sampling period
of T.sub.s=1/30,720,000 seconds. Time intervals of a communications
resource may be organized according to radio frames each having a
duration of 10 milliseconds (ms), where the frame period may be
expressed as T.sub.f=307,200 T.sub.s. The radio frames may be
identified by a system frame number (SFN) ranging from 0 to 1023.
Each frame may include 10 subframes numbered from 0 to 9, and each
subframe may have a duration of 1 ms. A subframe may be further
divided into 2 slots each having a duration of 0.5 ms, and each
slot may contain 6 or 7 modulation symbol periods (e.g., depending
on the length of the cyclic prefix prepended to each symbol
period). Excluding the cyclic prefix, each symbol period may
contain 2048 sampling periods. In some cases, a subframe may be the
smallest scheduling unit of the wireless communications system 100,
and may be referred to as a transmission time interval (TTI). In
other cases, a smallest scheduling unit of the wireless
communications system 100 may be shorter than a subframe or may be
dynamically selected (e.g., in bursts of shortened TTIs (sTTIs) or
in selected component carriers using sTTIs).
In some wireless communications systems, a slot may further be
divided into multiple mini-slots containing one or more symbols. In
some instances, a symbol of a mini-slot or a mini-slot may be the
smallest unit of scheduling. Each symbol may vary in duration
depending on the subcarrier spacing or frequency band of operation,
for example. Further, some wireless communications systems may
implement slot aggregation in which multiple slots or mini-slots
are aggregated together and used for communication between a UE 115
and a base station 105.
The term "carrier" refers to a set of radio frequency spectrum
resources having a defined physical layer structure for supporting
communications over a communication link 125. For example, a
carrier of a communication link 125 may include a portion of a
radio frequency spectrum band that is operated according to
physical layer channels for a given radio access technology. Each
physical layer channel may carry user data, control information, or
other signaling. A carrier may be associated with a pre-defined
frequency channel (e.g., an evolved universal mobile
telecommunication system terrestrial radio access (E-UTRA) absolute
radio frequency channel number (EARFCN)), and may be positioned
according to a channel raster for discovery by UEs 115. Carriers
may be downlink or uplink (e.g., in an FDD mode), or be configured
to carry downlink and uplink communications (e.g., in a TDD mode).
In some examples, signal waveforms transmitted over a carrier may
be made up of multiple sub-carriers (e.g., using multi-carrier
modulation (MCM) techniques such as orthogonal frequency division
multiplexing (OFDM) or discrete Fourier transform spread OFDM
(DFT-S-OFDM)).
The organizational structure of the carriers may be different for
different radio access technologies (e.g., LTE, LTE-A, LTE-A Pro,
NR). For example, communications over a carrier may be organized
according to TTIs or slots, each of which may include user data as
well as control information or signaling to support decoding the
user data. A carrier may also include dedicated acquisition
signaling (e.g., synchronization signals or system information,
etc.) and control signaling that coordinates operation for the
carrier. In some examples (e.g., in a carrier aggregation
configuration), a carrier may also have acquisition signaling or
control signaling that coordinates operations for other
carriers.
Physical channels may be multiplexed on a carrier according to
various techniques. A physical control channel and a physical data
channel may be multiplexed on a downlink carrier, for example,
using time division multiplexing (TDM) techniques, frequency
division multiplexing (FDM) techniques, or hybrid TDM-FDM
techniques. In some examples, control information transmitted in a
physical control channel may be distributed between different
control regions in a cascaded manner (e.g., between a common
control region or common search space and one or more UE-specific
control regions or UE-specific search spaces).
A carrier may be associated with a particular bandwidth of the
radio frequency spectrum, and in some examples the carrier
bandwidth may be referred to as a "system bandwidth" of the carrier
or the wireless communications system 100. For example, the carrier
bandwidth may be one of a number of predetermined bandwidths for
carriers of a particular radio access technology (e.g., 1.4, 3, 5,
10, 15, 20, 40, or 80 MHz). In some examples, each served UE 115
may be configured for operating over portions or all of the carrier
bandwidth. In other examples, some UEs 115 may be configured for
operation using a narrowband protocol type that is associated with
a predefined portion or range (e.g., set of subcarriers or RBs)
within a carrier (e.g., "in-band" deployment of a narrowband
protocol type).
In a system employing MCM techniques, a resource element may
consist of one symbol period (e.g., a duration of one modulation
symbol) and one subcarrier, where the symbol period and subcarrier
spacing are inversely related. The number of bits carried by each
resource element may depend on the modulation scheme (e.g., the
order of the modulation scheme). Thus, the more resource elements
that a UE 115 receives and the higher the order of the modulation
scheme, the higher the data rate may be for the UE 115. In MIMO
systems, a wireless communications resource may refer to a
combination of a radio frequency spectrum resource, a time
resource, and a spatial resource (e.g., spatial layers), and the
use of multiple spatial layers may further increase the data rate
for communications with a UE 115.
Devices of the wireless communications system 100 (e.g., base
stations 105 or UEs 115) may have a hardware configuration that
supports communications over a particular carrier bandwidth, or may
be configurable to support communications over one of a set of
carrier bandwidths. In some examples, the wireless communications
system 100 may include base stations 105 and/or UEs 115 that
support simultaneous communications via carriers associated with
more than one different carrier bandwidth.
Wireless communications system 100 may support communication with a
UE 115 on multiple cells or carriers, a feature which may be
referred to as carrier aggregation or multi-carrier operation. A UE
115 may be configured with multiple downlink component carriers and
one or more uplink component carriers according to a carrier
aggregation configuration. Carrier aggregation may be used with
both FDD and TDD component carriers.
In some cases, communication devices, such as UEs 115 or base
stations 105, may support MIMO mmW communications of two or more
MIMO streams via two or more beams. In some cases, a sequential
technique may be used for configuring MIMO communications, in which
analog RF beamforming parameters (e.g., analog beamforming
parameters for a number of frequency sub-bands) are determined
based on reference signal measurements during a beam sweeping
procedure in which a number of combinations of analog RF
beamforming parameters for two or more beams are transmitted. Then,
digital baseband beamforming parameters (e.g., digital beamforming
parameters for baseband signals that are not modulated on a carrier
frequency) may be determined and used for baseband processing of
the two or more MIMO streams. The digital baseband beamforming
parameters may include baseband precoding parameters used for
transmitting the two or more MIMO streams on the two or more beams,
and baseband combiner parameters used for receiving the two or more
MIMO streams on the two or more beams.
FIG. 2 illustrates an example of a wireless communications system
200 that supports multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure. The wireless communications system 200 may include a
base station 105-a and a UE 115-a within a geographic coverage area
110-a. The base station 105-a and the UE 115-a may be examples of
the corresponding devices described with reference to FIG. 1. In
some examples, the wireless communications system 200 may support
multiple radio access technologies including 4G systems such as LTE
systems, LTE-A systems, or LTE-A Pro systems, and 5G systems which
may be referred to as NR systems. In some examples, the wireless
communications system 200 may implement aspects of the wireless
communications system 100.
The wireless communications system 200 may, for example, be a MIMO
mmW system. The base station 105-a and the UE 115-a may thus
support directional communications. In some examples, directional
communications may include one or more of the base station 105-a
transmitting (or receiving on) one or more directional beams 205 or
the UE 115-a transmitting (or receiving) one or more directional
beams 210. In some examples, one or more directional beams 205 may
have a beam correspondence with one or more directional beams 210.
For example, a directional beam 205 and a directional beam 210 may
be a beam pair. The wireless communications system 200 may
therefore support improvements to power consumption, spectral
efficiency, higher data rates and, in some examples, may promote
high reliability and low latency for beamforming operations, among
other benefits.
In the example of FIG. 2, the base station 105-a and the UE 115-a
may perform a beamforming operation in accordance with one or more
codebooks to improve beamforming reliability and data rate for
directional communications. The codebooks may have a number N
possible beamforming vectors, where N may refer to a number of
antennas of the base station 105-a and the UE 115-a. In some
examples, N may be dependent on N.sub.T and N.sub.R, where N.sub.T
refers to a number of transmit antennas (e.g., of the base station
105-a) and N.sub.R refers to a number of receive antennas (e.g., of
the UE 115-a). In some examples, the beamforming operation may
involve the base station 105-a identifying, in accordance with the
codebooks, an f.sub.n that results in a metric satisfying a
threshold, where f.sub.n is a beamforming vector. Similarly, the
beamforming operation may involve the UE 115-a identifying, in
accordance with the codebooks, a w.sub.m that results in a metric
satisfying a threshold, where w.sub.m is a beamforming combining
vector.
The metric may, in some examples, include a signal strength, and
the signal strength may be dependent on w*.sub.mHf.sub.n, where H
is a channel 215 associated with the directional communications
between the base station 105-a and the UE 115-a, and w.sub.m and
f.sub.n are the best beamforming vectors for H. Therefore,
w*.sub.mHf.sub.n may be defined as an effective channel. The base
station 105-a and the UE 115-a may thus identify and select a
directional beam pair (e.g., (f.sub.n, w.sub.m)) for directional
communications (i.e., a single beam approach). In some examples, to
enable multi-stream operation, one or more of the base station
105-a or the UE 115-a may determine and select multiple transmit
directional beams and receive directional beams. For example, the
base station 105-a may determine and select multiple directional
beams 205, which may correspond to one or more of transmit
directional beams or receive directional beams. In some other
examples, the UE 115-a may determine and select multiple
directional beams 210, which may correspond to one or more of
transmit directional beams or receive directional beams. The
multiple transmit directional beams and receive directional beams
may be used simultaneously at one or more of the base station 105-a
or the UE 115-a. Additionally, in some examples, the various
directional beams may be from a same or different panel of one or
more of the base station 105-a or the UE 115-a. For example, one or
more of the base station 105-a or the UE 115-a may be configured
with multiple panels, and each panel may include an array of same
or different antennas (e.g., one or more of N.sub.T or
N.sub.R).
In some examples, one or more of the base station 105-a or the UE
115-a may perform a search over a number of possible beamforming
pairs (f.sub.n, w.sub.m). As demand for communication efficiency
increases, it may be desirable for one or more of the base station
105-a or the UE 115-a to target low latencies and improve
reliability for beamforming operations, and more specifically to
perform a sequential technique to determine wideband and baseband
beamforming parameters (e.g., to select two or more beamforming
pairs (f.sub.n, w.sub.m), or beam weights).
FIG. 3 illustrates an example of a wireless communications system
300 that supports multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure. The wireless communications system 300 may include a
base station 105-b and a UE 115-b, which may be examples of the
corresponding devices described with reference to FIGS. 1 and 2. In
some examples, the wireless communications system 300 may implement
aspects of the wireless communications systems 100 and 200. For
example, one or more of the base station 105-b or the UE 115-b may
support improvements to power consumption, spectral efficiency,
higher data rates and, in some examples, may promote high
reliability and low latency for beamforming operations, among other
benefits.
The base station 105-b may include components for directional
communications including components for transmitting and receiving
directional communications, including a radio frequency (RF) chain
305 (N.sub.RF.sup.T), an analog beamforming F.sub.RF component 310,
and one or more physical transmit antennas 315. These components
may be in electronic communication via one or more buses of the
base station 105-b. Additionally, in some examples, these
components can be implemented, at least in part, by one or both of
a modem and a processor of the base station 105-b. The UE 115-b
may, additionally, include components for directional
communications including components for transmitting and receiving
directional communications, including one or more physical receive
antennas 325, an analog beamforming W.sub.RF component 330, and an
RF chain 335 (N.sub.RF.sup.R). These components may be in
electronic communication via one or more buses of the UE 115-b.
Additionally, in some examples, these components can be
implemented, at least in part, by one or both of a modem and a
processor of the UE 115-b. While various examples provided herein
may refer to a base station 105 as a transmitting device and a UE
115 as a receiving device, it is to be understood that a UE 115 may
be a transmitting device and a base station 105 may be a receiving
device and operate in accordance with various techniques discussed
herein.
The base station 105-b and the UE 115-b may perform a beamforming
operation in accordance with one or more codebooks to provide beams
with suitable reliability and data rate for directional
communications. The codebooks may have a number N possible
beamforming vectors. In some examples, N may be dependent on
N.sub.T and N.sub.R, where N.sub.T refers to a number of physical
transmit antennas 315 of the base station 105-b and N.sub.R refers
to a number of physical receive antennas 325 of the UE 115-b.
In some examples, two or more beams may be selected for
transmission of two or more MIMO streams based on a channel metric
associated with different combinations of beams from which the two
or more beams may be selected. The metric maybe a signal strength,
and the signal strength may be dependent on a multi-path channel
320 (H) associated with the directional communications between the
base station 105-b and the UE 115-b. In some examples, one or more
of the base station 105-b or the UE 115-b may determine an
effective channel of the multi-path channel 320 (H) with respect to
one or more of the analog beamforming F.sub.RF component 310 or the
analog beamforming W.sub.RF component 330. In other words, the full
multi-path channel 320 (H) is unknown to one or more of the base
station 105-b or the UE 115-b. One or more of the base station
105-b or the UE 115-b may determine and select a directional beam
pair (e.g., (f.sub.n, w.sub.m)) for directional communications
based on the effective channel, and in accordance with, the analog
beamforming F.sub.RF component 310 or the analog beamforming
W.sub.RF component 330. Thus, without the analog processing blocks
(e.g., the analog beamforming F.sub.RF component 310 or the analog
beamforming W.sub.RF component 330), a link between the base
station 105-b and the UE 115-b cannot be established.
The analog beamforming F.sub.RF component 310 may correspond to a
number of directional beams. For example, the analog beamforming
F.sub.RF component 310 may be defined by the following matrix:
F.sub.RF=[f.sub.1 f.sub.2 . . . f.sub.N.sub.RF.sub.T], where
f.sub.1 f.sub.2 . . . f.sub.N.sub.RF.sub.T are beamforming vectors
of the beamforming matrix F.sub.RF. In other words, each element f
may correspond to a directional beam of a number of directional
beams. The analog beamforming W.sub.RF component 330 may also
correspond to a number of directional beams. For example, the
analog beamforming W.sub.RF component 330 may be defined by the
following matrix: W.sub.RF=[w.sub.1 w.sub.2 . . .
w.sub.N.sub.RF.sub.T], where w.sub.1 w.sub.2 . . .
w.sub.N.sub.RF.sub.T are beamforming vectors of the beamforming
matrix W.sub.RF. In other words, each element w may correspond to a
directional beam of a number of directional beams. In some
examples, an improper determination and selection of F.sub.RF and
W.sub.RF, by the base station 105-b and/or the UE 115-b, may change
one or more rank properties of the effective channel, and
beamforming operations may as a result not be improved (e.g., data
rate) relative to non-MIMO communications.
FIG. 4 illustrates an example of a wireless communications system
400 that supports multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure. The wireless communications system 400 may include a
base station 105-c and a UE 115-c, which may be examples of the
corresponding devices described with reference to FIGS. 1 through
3. In some examples, the wireless communications system 400 may
implement aspects of the wireless communications systems 100
through 300. For example, one or more of the base station 105-c or
the UE 115-c may support improvements to power consumption,
spectral efficiency, higher data rates and, in some examples, may
promote high reliability and low latency for beamforming
operations, among other benefits.
The base station 105-c may include components for directional
communications including components for transmitting and receiving
directional communications, including a precoder 410 (e.g., a
baseband precoding component), an RF chain 415 (N.sub.RF.sup.T), a
wideband or analog beamforming F.sub.RF component 420, and one or
more physical transmit antennas 425 (N.sub.T). These components may
be in electronic communication via one or more buses of the base
station 105-c. Additionally, in some examples, these components can
be implemented, at least in part, by one or both of a modem and a
processor of the base station 105-c. In some examples, the UE 115-c
may, additionally or alternatively, be configured with one or more
of the components, such as the precoder 410, the RF chain 415
(N.sub.RF.sup.T), the analog beamforming F.sub.RF component 420,
and the one or more physical transmit antennas 425 (N.sub.T), when
the UE 115-c acts as the transmitting device.
The UE 115-c may, additionally, include components for directional
communications including components for transmitting and receiving
directional communications, including one or more physical receive
antennas 435, an analog beamforming W.sub.RF component 440, an RF
chain 445 (N.sub.RF.sup.R), and a combiner 450. These components
may be in electronic communication via one or more buses of the UE
115-c. Additionally, in some examples, these components can be
implemented, at least in part, by one or both of a modem and a
processor of the UE 115-c. In some examples, the base station 105-c
may, additionally or alternatively, be configured with one or more
of the components, such as the one or more physical receive
antennas 435, the analog beamforming W.sub.RF component 440, the RF
chain 445 (N.sub.RF.sup.R), and the combiner 450, when the base
station 105-c acts as the receiving device.
In some examples, one or more of the base station 105-c or the UE
115-c may communicate directional communications on a wideband
(e.g., over an entire bandwidth) or one or more subbands. A number
of RF chains available for MIMO operations for one or more of the
base station 105-c or the UE 115-c may be defined by the following
expression: N.sub.RF.ltoreq.min(N.sub.T, N.sub.R). In some
examples, a precoder (e.g., for downlink directional
communications) or a combiner (e.g., for uplink directional
communications) at the base station 105-c may determine a
beamforming matrix F.sub.RF as F.sub.RF.di-elect
cons.C.sup.N.sup.T.sup..times.N.sup.RF, and each column
f.sub.RF.di-elect cons.F.sub.RF.sup.v (i.e., the (analog) codebook
at the base station 105-c). In some examples, a combiner (e.g., for
downlink directional communications) or a precoder (e.g., for
uplink directional communications) at the UE 115-c may determine a
beamforming matrix W.sub.RF as W.sub.RF.di-elect
cons.C.sup.N.sup.R.sup..times.N.sup.RF, and each column
w.sub.RF.di-elect cons.W.sub.RF.sup.v (i.e., the (analog) codebook
at the UE 115-c). Thus, (f.sub.RF.di-elect cons.F.sub.RF.sup.v,
w.sub.RF.di-elect cons.W.sub.RF.sup.v) may an analog beamforming
pair for single-input single-output (SISO) operation.
One or more of the base station 105-c or the UE 115-c may determine
a beamforming pair for a transmit analog precoder (e.g., downlink:
F.sub.RF, uplink: W.sub.RF) and beamforming pair for a receive
combiner (e.g., downlink: W.sub.RF, uplink: F.sub.RF). In some
examples, one or more of the base station 105-c or the UE 115-c may
determine the beamforming pairs using one or more reference
signals. For example, one or more of the base station 105-c or the
UE 115-c may determine the beamforming pairs using one or more
downlink reference signals or uplink reference signals. Examples of
downlink reference signals include a channel state information
(CSI) reference signal (CSI-RS), a synchronization signal block
(SSB), and the like. Examples of uplink reference signals include a
sounding reference signal (SRS), and the like. In some examples,
downlink and uplink can use either the same reference signal or
different reference signals. In some examples, if downlink
reference signals are used, the UE 115-c may determine the best
F.sub.RF and W.sub.RF, and report the best F.sub.RF to the base
station 105-c. Similarly, if uplink reference signals are used, the
base station 105-c may determine the best F.sub.RF and W.sub.RF,
and report the best W.sub.RF to the UE 115-c.
In some examples, the base station 105-c may receive, at the
precoder 410, one or more MIMO streams 405 (N.sub.S). In some
examples, one or more of the base station 105-c or the UE 115-c may
be capable of supporting a number of MIMO streams (N.sub.S)
depending on a number of RF chains. In other words, one or more of
the base station 105-c or the UE 115-c may be configured to support
a number of MIMO streams (N.sub.S) according to the following
expression: N.sub.S.ltoreq.N.sub.RF. The precoder 410 may process
the one or more MIMO streams 405 (N.sub.S) by performing one or
more baseband beamforming related operations, such as a digital
beamforming operation, an inverse fast Fourier transform (IFFT)
operation, or a digital-to-analog conversion (DAC) operation, among
other examples. The precoder 410 may then forward, via the RF chain
415, the processed one or more MIMO streams 405 (e.g., in the form
of packets) to the wideband (e.g., analog) beamforming F.sub.RF
component 420. The analog beamforming F.sub.RF component 420 may
determine and select one or more directional beams (e.g., based on
one or more beamforming elements of a beamforming matrix W.sub.RF
provided by the UE 115-c, or by referencing a codebook) and map
them to the one or more physical transmit antennas 425 for
transmitting to the UE 115-c over a multi-path channel 430.
The UE 115-c may receive one or more packets (e.g., associated with
the processed one or more MIMO streams 405) on the one or more
physical receive antennas 435. In some examples, the UE 115-c may
receive and perform a de-mapping operation via the analog
beamforming W.sub.RF component 440 (e.g., based on one or more
beamforming elements of a beamforming matrix F.sub.RF provided by
the base station 105-c, or by referencing a codebook). The analog
beamforming W.sub.RF component 440 may forward the one or more
packets to the RF chain 445, which may then forward the one or more
packets to the combiner 450. The combiner 450 may process the one
or more packets (e.g., in the form of packets) by performing one or
more beamforming related operations, such as a digital baseband
processing beamforming operation, a fast Fourier transform (FFT)
operation, or an analog-to-digital conversion (ADC) operation,
among other examples. The combiner 450 may then output the one or
more packets in the form of one or more MIMO streams 455.
Additionally or alternatively, one or more of the base station
105-c or the UE 115-c may determine one or more beamforming pairs
for a transmit baseband precoder (e.g., downlink: F.sub.BBS[k],
uplink: W.sub.BBS[k]) or a receive baseband combiner (e.g.,
downlink: W.sub.BBS[k], uplink: F.sub.BBS[k]). A baseband precoder
(for downlink) or a baseband combiner (for uplink) at the base
station 105-c may thus be defined by the following expression:
F.sub.BB[k].di-elect cons.C.sup.N.sup.RF.sup..times.N.sup.S.
Similarly, a baseband combiner (for downlink) or a baseband
precoder (for uplink) at the UE 115-c may be defined by the
following expression: W.sub.BB[k].di-elect
cons.C.sup.N.sup.RF.sup..times.N.sup.S. The effective
precoder/combiner at the base station 105-c may thus be represented
by the following expression: F.sub.T[k]=F.sub.RFF.sub.BB[k], and
the effective combiner/precoder at the UE 115-c may be represented
by the following expression: W.sub.R[k]=W.sub.RFW.sub.BB[k]. In
some examples, one or more of the precoder 410 or the combiner 450
may be dependent on a subband or a subcarrier (e.g., OFDM
subcarrier) or a multi-tap for single carrier implementations. In
some examples, k may be a subband value from 1 to N.sub.SB, for
example a subband or a subcarrier index (e.g., OFDM subcarrier
index) or a tap index in single carrier implementations.
In some examples, a baseband received signal vector at a subband k
may be defined by the following equation:
y[k]=W*.sub.BB[k]W*.sub.RFH[k]F.sub.RFF.sub.BB[k]s[k]+W*.sub.BB[k]W*.sub.-
RFn[k] (1) for k=1, . . . , N.sub.SB, where H[k] is the multi-path
channel 430 at subband k, s[k] is a transmit signal at subband
index k (e.g., a signal transmitted by the base station 105-c),
F.sub.RFF.sub.BB[k] is the precoder 410 at a transmitting-side
(e.g., at the base station 105-c), and W*.sub.BB[k]W*.sub.RF is the
combiner 450 at a receiving-side (e.g., at the UE 115-c). In some
examples, the W*.sub.RF and the F.sub.RF are wideband, radio
frequency BF (i.e., common for all k) while the W*.sub.BB[k] and
the F.sub.BB[k] are subband baseband BF (i.e., dependent on subband
index k). In some examples, n[k] may be noise at a subband index k.
The noise n[k] at a subband index k may be Gaussian noise. In some
other examples, the noise n[k] at a subband index k may be thermal
noise, intermodulation noise, electronic noise, quantum noise,
among other examples.
One or more of the base station 105-c or the UE 115-c may support
improvements in determining mutual information (MI) (e.g.,
maximizing an achievable rate) for a (radio frequency) codebook. In
some examples, one or more of the base station 105-c or the UE
115-c may determine the mutual information in accordance with the
following equation:
.times..times..times..times..times..function..times. ##EQU00001##
where H[k]=W*.sub.BB[k]W*.sub.RFH[k]F.sub.RFF.sub.BB[k], SNR is the
signal-to-noise ratio, and N.sub.S corresponds to one or more
streams (e.g., MIMO streams) and |A| stands for the determinant of
square matrix A. This equation assumes the analog and baseband
combiners are designed such that the noise variance is an identity
matrix, and techniques as discussed herein also provides such a
property. In some examples, one or more of the base station 105-c
or the UE 115-c may determine the mutual information for
F.sub.BB[1], . . . , F.sub.BB[N.sub.SB] and W.sub.BB[1], . . . ,
W.sub.BB[N.sub.SB]. One or more of the base station 105-c or the UE
115-c may determine the mutual information, in some examples, such
that F.sub.RF.di-elect cons.F.sub.RF and W.sub.RF.di-elect
cons.W.sub.RF, where F.sub.RF is an analog codebook for F.sub.RF
and where W.sub.RF is an analog codebook for W.sub.RF.
FIG. 5 illustrates an example of a wireless communications system
500 that supports multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure. The wireless communications system 500 may include a
base station 105-d and a UE 115-d, which may be examples of the
corresponding devices described with reference to FIGS. 1 through
4. In some examples, the wireless communications system 500 may
implement aspects of the wireless communications systems 100
through 400. For example, one or more of the base station 105-d or
the UE 115-d may support improvements to power consumption,
spectral efficiency, higher data rates and, in some examples, may
promote high reliability and low latency for beamforming
operations, among other benefits.
The base station 105-d may include components for directional
communications including components for transmitting and receiving
directional communications, including a precoder 510, RF chains 515
(N.sub.RF.sup.T) (corresponding to number of a transceiver units
(TXRUs)), an analog beamforming F.sub.RF component 520, and one or
more physical transmit antennas 525 (N.sub.T). These components may
be in electronic communication via one or more buses of the base
station 105-d. Additionally, in some examples, these components can
be implemented, at least in part, by one or both of a modem and a
processor of the base station 105-d. In some examples, the UE 115-d
may, additionally or alternatively, be configured with one or more
of the components, such as the precoder 510, RF chains 515
(N.sub.RF.sup.T) (corresponding to number of a transceiver units
(TXRUs)), the analog beamforming F.sub.RF component 520, and the
one or more physical receive antennas 525 (N.sub.T), when the UE
115-d acts as the transmitting device.
The UE 115-d may, additionally, include components for directional
communications including components for transmitting and receiving
directional communications, including one or more physical receive
antennas 535, an analog beamforming W.sub.RF component 540, an RF
chain 545 (N.sub.RF.sup.R), and a combiner 550. These components
may be in electronic communication via one or more buses of the UE
115-d. Additionally, in some examples, these components can be
implemented, at least in part, by one or both of a modem and a
processor of the UE 115-d. In some examples, the base station 105-d
may, additionally or alternatively, be configured with one or more
of the components, such as the one or more physical receive
antennas 535, the analog beamforming W.sub.RF component 540, the RF
chain 545 (N.sub.RF.sup.R), and the combiner 550, when the base
station 105-d acts as the receiving device.
In some examples, the base station 105-d may receive, at the
precoder 510, one or more MIMO streams 505 (N.sub.S). In some
examples, one or more of the base station 105-d or the UE 115-d may
be capable of supporting a number of MIMO streams (N.sub.S)
depending on a number of RF chains. In other words, one or more of
the base station 105-d or the UE 115-d may be configured to support
a number of MIMO streams (N.sub.S) according to the following
expression: N.sub.S.ltoreq.N.sub.RF. The precoder 510 may process
the one or more MIMO streams 505 (N.sub.S) by performing one or
more beamforming related operations, such as a digital beamforming
operation, an IFFT operation, or a DAC operation, among other
examples. The precoder 510 may then forward, via the RF chain 515,
the processed one or more MIMO streams 505 (e.g., in the form of
packets) to the analog beamforming F.sub.RF component 520. The
analog beamforming F.sub.RF component 520 may determine and select
one or more directional beams (e.g., based on one or more
beamforming elements of a beamforming matrix W.sub.RF provided by
the UE 115-d, or by referencing a codebook) and map them to the one
or more physical transmit antennas 525 for transmitting to the UE
115-d over a multi-path channel 530 (e.g., also referred to as
H[k]). In some examples, a baseband effective channel at a subband
k may be defined by the following expression:
H.sub.eff[k]=W*.sub.BBWW*.sub.RFH[k]F.sub.RFF.sub.BBW.
The UE 115-d may receive one or more packets (e.g., associated with
the processed one or more MIMO streams 505) on the one or more
physical receive antennas 535. In some examples, the UE 115-d may
receive and perform a de-mapping operation via the analog
beamforming W.sub.RF component 540 (e.g., based on one or more
beamforming elements of a beamforming matrix F.sub.RF provided by
the base station 105-d, or by referencing a codebook). The analog
beamforming W.sub.RF component 540 may forward the one or more
packets to the RF chain 545, which may then forward the one or more
packets to the combiner 550. The combiner 550 may process the one
or more packets (e.g., in the form of packets) by performing one or
more beamforming related operations, such as a digital processing
beamforming operation, a FFT operation, or a ADC operation, among
other examples. The combiner 550 may then output the one or more
packets in the form of one or more MIMO streams 555.
One or more of the base station 105-d or the UE 115-d may determine
one or more beamforming pairs for a transmit baseband precoder
(e.g., downlink: F.sub.BBS[k], uplink: W.sub.BBS[k]) or a receive
baseband combiner (e.g., downlink: W.sub.BBS[k], uplink:
F.sub.BBS[k]). In some examples, one or more of the base station
105-d or the UE 115-d may determine a F.sub.RF and an W.sub.RF,
which may be wideband BF (i.e., common for all subband indices k).
In some examples, one or more of the base station 105-d or the UE
115-d may determine a F.sub.BBW and an W.sub.BBW, which may be
wideband BF (i.e., at a subband index k).
In some examples, one or more of the base station 105-d or the UE
115-d may determine one or more of F.sub.RF, F.sub.BBW,
F.sub.BBS[k], W.sub.RF, W.sub.BBW, and W.sub.BBS[k] sequentially
for all subcarriers k. For example, one or more of the base station
105-d or the UE 115-d may initially determine F.sub.RF and
W.sub.RF. In some examples, F.sub.BBW and W.sub.BBW may depend
exclusively on F.sub.RF and W.sub.RF. For example, the base station
105-d may determine F.sub.BBW based on the following expressions:
F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2, and the UE 115-d may
determine W.sub.BBW based on the following expressions:
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. In some examples, F.sub.RF
and W.sub.RF may be exclusively dependent on H[k]'s (i.e., the
multi-path channel 530 at subbands indices k). One or more of the
base station 105-d or the UE 115-d may thus determine a beamforming
pair {F.sub.RF, W.sub.RF} according to the following equation:
.di-elect cons..di-elect
cons..times..times..times..times..times..times..times..lamda..function..t-
imes..times..times..function..times..function..times..times..times.
##EQU00002## where .lamda..sub.j(A) denotes the j-th singular value
of A. In some examples, the equation (3) may be simplified to the
following equation:
.di-elect cons..di-elect
cons..times..times..times..times..times..times..times..lamda..function..f-
unction. ##EQU00003## where H.sub.eff[k] is
((W*.sub.RFW.sub.RF).sup.-1/2W*.sub.RFH[k]F.sub.RF(F*.sub.RFF.sub.RF).sup-
.-1/2). Once one or more of the base station 105-d or the UE 115-d
determine F.sub.RF, W.sub.RF, one or more of the base station 105-d
or the UE 115-d may determine F.sub.BBS[k] and W.sub.BBS[k], which
may depend exclusively on H.sub.eff[k]. As such, F.sub.BBS[k] and
W.sub.BBS[k] may be the matrices composed of the dominant N.sub.S
right and left singular vectors of H.sub.eff[k]'s.
In some examples, the determining {F.sub.RF, W.sub.RF} may involve
one or more of the base station 105-d or the UE 115-d performing a
search according to a beam training procedure. The following is an
example search for determining F.sub.RF and W.sub.RF at the base
station 105-d and the UE 115-d without knowing H[k] explicitly. For
example, one or more of the base station 105-d or the UE 115-d may
use a beam sweeping operation (i.e., by testing a set of possible
codebook candidates) for F.sub.RF and W.sub.RF. In other words, one
or more of the base station 105-d or the UE 115-d may use a beam
sweeping operation to determine candidates F.sub.RF and W.sub.RF
using the equation (3). As such, one or more of the base station
105-d or the UE 115-d may determine F.sub.RF.di-elect
cons.F.sub.RF={F.sub.RF,1, . . . , F.sub.RF,P} and
W.sub.RF.di-elect cons.W.sub.RF={W.sub.RF,1, . . . , W.sub.RF,Q}.
In some examples, the elements (i.e., {F.sub.RF,1, . . . ,
F.sub.RF,P}) in F.sub.RF may be referred to as p-elements, while
the elements (i.e., {W.sub.RF,1, . . . , W.sub.RF,Q}) in W.sub.RF
may be referred to as q-elements. Accordingly, by determining
mutual information for all possible PQ combinations of (p, q), one
or more of the base station 105-d or the UE 115-d may determine (or
obtain) a best solution p.sub.best and q.sub.best.
In some cases, the determination of p.sub.best and q.sub.best may
be performed as a first stage in a sequential technique for
determining MIMO beamforming parameters. The first stage in such
techniques may provide for determination of a transmission analog
precoder (i.e., DL: F.sub.RF, UL: W.sub.RF) and receive analog
combiner (i.e., DL: W.sub.RF, UL: F.sub.RF). The beam sweeping
operation may be performed using downlink reference signals (e.g.,
CSI-RS, SSB, etc.), uplink reference signals (e.g. SRS, etc.), or
combinations thereof. In cases that use a downlink reference
signal, the UE 115-d may determine a preferred F.sub.RF and
W.sub.RF and report the determined F.sub.RF to the base station
105-d. In cases that use an uplink reference signal, the base
station 105-d may determine the F.sub.RF and W.sub.RF and reports
the determined W.sub.RF to the UE 115-d. In some cases, the
downlink and uplink may use either the same reference signal or
different reference signals.
Following the first stage, a second stage may include determination
of a transmission baseband precoder (i.e., DL: F.sub.BBS[k], UL:
W.sub.BBS[k]). Such a determination may, in some cases, reuse the
results of the first stage without any additional reference signal
transmissions. In other cases, one or more additional downlink or
uplink reference signals may be used. Following the second stage a
third stage may include determination of a receive baseband
combiner (i.e., DL: W.sub.BBS[k], UL: F.sub.BBS[k]). In some cases,
a demodulation reference signal (DMRS) transmitted with a shared
channel transmission (e.g., PDSCH, PUSCH) may be used to determine
the baseband combiner.
With reference to the first stage, various techniques provide for
determination of F.sub.RF and W.sub.RF at the base station 105-d
and the UE 115-d without knowing H[k]'s explicitly, such as the
technique discussed above with reference to Equations (3) and (4)
using beam sweeping at both the base station 105-d and UE 115-d,
i.e., by testing all possible combinations of candidates of
codebooks .sub.RF={F.sub.RF,1, . . . , F.sub.RF,P} and
.sub.RF={W.sub.RF,1, . . . , W.sub.RF,Q}, such that in Equations
(3) and (4) F.sub.RF.di-elect cons..sub.RF={F.sub.RF,1, . . . ,
F.sub.RF,P}, W.sub.RF.di-elect cons..sub.RF={W.sub.RF,1, . . . ,
W.sub.RF,Q}. By calculating MI metrics for all possible PQ
combinations of (p, q), the solution, p.sub.best and q.sub.best,
can be obtained and reported as needed. In some cases, it is
possible Q=1 (i.e., only base station 105-d does beam sweeping) or
P=1 (i.e., only UE 115-d does beam sweeping). The reference signal
used for the beam sweeping may include, for example, CSI-RS for
downlink reference signals or SRS for uplink reference signals.
A first option may include using downlink reference signals for
beam sweeping. In such cases, the base station 105-d transmits a
number of reference signals (e.g., CSI-RS) for each combination of
P and Q in the configured codebooks. The UE 115-d may receive and
measure the reference signals, calculate the MI metric, and find an
acceptable or optimal F.sub.RF(=F.sub.RF,p.sub.best) and W.sub.RF
(=W.sub.RF,q.sub.best). The UE 115-d may then report p.sub.best to
the base station 105-d, noting that if P=1 this is not needed. In
some cases, the report of p.sub.best may be an indication of a
codebook index in .sub.RF associated with p.sub.best. A second
option may include using uplink reference signals for beam
sweeping. In such cases, the UE 115-d transmits a number of uplink
reference signals (e.g., SRS) for each combination of P and Q in
the configured codebooks. The base station 105-d may then receive
and measure the reference signals, calculate the MI metric, and
find an acceptable or optimal F.sub.RF(=F.sub.RF,p.sub.best) and
W.sub.RF (=W.sub.RF,q.sub.best). The base station 105-d may then
reports q.sub.best to the UE 115-d, noting that if Q=1, this is not
needed. In some cases, the report of p.sub.best may be an
indication of a codebook index in .sub.RF associated with
q.sub.best. The downlink and uplink determinations may use either
the same reference signal or different reference signals (e.g.,
DL-RS is used for DL and UL, UL-RS is used for DL and UL, or DL-RS
is used for DL and UL-RS is used for UL).
In the second stage, the transmission baseband precoder (DL:
F.sub.BBS[k], UL: W.sub.BBS[k]) may be determined. In cases where
the baseband precoder is determined for downlink transmissions, and
downlink reference signals are used, and measured at the UE 115-d,
the base station 105-d will not know the effective channel
H.sub.eff[k] with respect to the determined F.sub.RF and W.sub.RF,
as this is only known at the UE 115-d at this point. In some cases,
the UE 115-d may transmit an uplink reference signal (e.g., SRS)
using the determined W.sub.RF, and the base station 105-d then
estimates the effective baseband channel H.sub.eff[k] by based on
measurements of the uplink reference signal using the signaled
F.sub.RF (i.e., F.sub.RF,pbest) that was signaled in the first
stage and F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. The base station
105-d then determines the transmission baseband precoder
F.sub.BBS[k] based on H.sub.eff[k]. In cases where uplink reference
signals are used at the first stage, and measured at the base
station 105-d, the base station 105-d will know the effective
channel H.sub.eff[k] with respect to the determined F.sub.RF and
W.sub.RF, and thus no additional reference signal is required, and
the base station 105-d determines the transmission baseband
precoder F.sub.BBS[k] based on H.sub.eff[k].
In cases where the baseband precoder is determined for uplink
transmissions, and when downlink reference signals are used in the
first stage, the UE 115-d will know the effective channel
H.sub.eff[k] with respect to the best F.sub.RF and W.sub.RF, no
additional reference signal is required, and the UE 115-d
determines the transmission baseband precoder W.sub.BBS[k] based on
H.sub.eff[k]. In cases where an uplink reference signal is used in
the first stage, the UE 115-d does not know the effective channel
H.sub.eff[k] with respect to the determined F.sub.RF and W.sub.RF,
and the base station 105-d may transmit a downlink reference signal
(e.g., CSI-RS) using the determined F.sub.RF. The UE 115-d may
receive and measure the downlink reference signal and estimate the
effective baseband channel H.sub.eff[k] by using the signaled
W.sub.RF (i.e., W.sub.RF,qbest) that was signaled in the first
stage and W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. The UE 115-d then
determines the transmission baseband precoder W.sub.BBS[k] based on
H.sub.eff[k].
In the third stage, the determination of the receive baseband
combiner (i.e., DL: W.sub.BBS[k], UL: F.sub.BBS[k]) may be
performed based on a reference signal (e.g., DMRS) transmitted with
a shared channel transmission for both uplink and downlink. In some
cases, the transmitter (i.e., DL: base station 105-d, UL: UE 115-d)
may send DMRS by using the determined analog and baseband precoder
(i.e., DL: F.sub.RF and F.sub.BBS[k], UL: W.sub.RF and
W.sub.BBS[k]). The receiver (i.e., DL: UE 115-d, UL: base station
105-d) may estimate the effective channel H.sub.eff[k] by using the
determined analog combiner (i.e., DL: W.sub.RF, UL: F.sub.RF) via
DMRS. The receiver may then determine the receive baseband combiner
(i.e., DL: W.sub.BBS[k], UL: F.sub.BBS[k]) based on H.sub.eff[k].
The receiver may then decode the shared channel transmission (e.g.,
PDSCH or PUSCH) by using the determined receive baseband combiner
(DL: W.sub.BBS[k], UL: F.sub.BBS[k]). While examples discussed
herein refer to DMRS, additionally or alternatively it is possible
to use an explicit reference signal. Examples of such sequential
techniques are illustrated in FIGS. 6 through 11.
FIG. 6 illustrates an example of a process flow 600 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The process flow
600 may illustrate a beam training technique and sequential
approach for determining MIMO beamforming parameters for two or
more beams using a number of downlink reference signals, and an
uplink reference signal. In some examples, the process flow 600 may
implement aspects of the wireless communications systems 100
through 500, as described with reference to FIGS. 1 through 5. For
example, the process flow 600 may be based on a configuration by a
base station 105 or a UE 115, and implemented for reduced power
consumption, spectral efficiency, higher data rates and, in some
examples, may promote high reliability and low latency for
beamforming operations, among other benefits.
The process flow 600 may include a base station 105-e and a UE
115-e, which may be examples of base stations 105 and UEs 115 as
described with reference to FIGS. 1 through 5. In the following
description of the process flow 600, the operations between the
base station 105-e and the UE 115-e may be transmitted in a
different order than the example order shown, or the operations
performed by the base station 105-e and the UE 115-e may be
performed in different orders or at different times. Some
operations may also be omitted from the process flow 600, and other
operations may be added to the process flow 600.
In this example, the process flow 600 includes multiple stages, in
accordance with the discussion of FIG. 5, including a first stage
605 for determination of a transmission analog precoder (F.sub.RF)
and a receive analog combiner (W.sub.RF), a second stage 610 for
determination of a transmission baseband precoder (F.sub.BBS[k]),
and a third stage 615 for determination of a receive baseband
combiner (W.sub.BBS[k]).
In this example, the first stage 605, the process flow 600 may
commence at 620 with the base station 105-e transmitting a CSI-RS
using F.sub.RF=F.sub.RF,1 and
F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. At 625, the UE 115-e may
receive the CSI-RS using W.sub.RF=W.sub.RF,1 and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. This may be repeated for
other combinations of p and q, at 630, until a last CSI-RS
transmission at 635 and a corresponding reception at 640. At 645,
the UE 115-e may estimate H.sub.eff[k] for all p and q. In some
examples, the UE 115-e may estimate H.sub.eff[k] to be
W*.sub.BBWW*.sub.RF[K]F.sub.RFF.sub.BBW for all p and q. Thus, the
base station 105-e may select a p-element from a codebook F.sub.RF,
for example, p=1, and transmit the CSI-RS on a directional beam
corresponding to p=1. Similarly, the UE 115-e may select a
q-element from a codebook W.sub.RF, for example, q=1, and receive
the CSI-RS on a directional beam corresponding to q=1. This is
performed for the combinations PQ, and at 650, the UE 115-e may
determine a best or preferred F.sub.RF,p.sub.best and a
W.sub.RF,q.sub.best, based on the different estimates (e.g., that
maximize MI). At 655, the UE 115-e may report the p.sub.best to the
base station 105-e.
At the second stage 610, the baseband precoder is determined. In
this example, at 660, the UE 115-e may transmit a SRS using
W.sub.RF=W.sub.RF,q.sub.best and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. The base station 105-e, at
665, may receive the SRS and at 670 estimate H.sub.eff[k] to be
W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW. At 675, the base station
105-e may determine F.sub.BBS[k] based on H.sub.eff[k].
At the third stage 615, the base station 105-e may transmit, at
680, a PDSCH transmission using F.sub.RF,p.sub.best, F.sub.BBS[k],
and F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. At 685, the UE 115-e
may receive the PDSCH using W.sub.RF,q.sub.best, W.sub.BBS[k], and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. At 690, the UE 115-e may
estimate H.sub.eff[k] based on the DMRS (i.e.,
W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW). At 695, the UE 115-e may
determine W.sub.BBS[k] based on H.sub.eff[k]. At 697, the UE 115-e
may decode the PDSCH using W.sub.BBS[k] at the receive
combiner.
FIG. 7 illustrates an example of a process flow 700 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The process flow
700 may illustrate a beam training technique and sequential
approach for determining MIMO beamforming parameters for two or
more beams using a number of downlink reference signals, and an
uplink reference signal. In some examples, the process flow 700 may
implement aspects of the wireless communications systems 100
through 500, as described with reference to FIGS. 1 through 5. For
example, the process flow 700 may be based on a configuration by a
base station 105 or a UE 115, and implemented for reduced power
consumption, spectral efficiency, higher data rates and, in some
examples, may promote high reliability and low latency for
beamforming operations, among other benefits.
The process flow 700 may include a base station 105-f and a UE
115-f, which may be examples of base stations 105 and UEs 115 as
described with reference to FIGS. 1 through 5. In the following
description of the process flow 700, the operations between the
base station 105-f and the UE 115-f may be transmitted in a
different order than the example order shown, or the operations
performed by the base station 105-f and the UE 115-f may be
performed in different orders or at different times. Some
operations may also be omitted from the process flow 700, and other
operations may be added to the process flow 700.
In this example, the process flow 700 includes multiple stages for
uplink MIMO transmissions, in accordance with the discussion of
FIG. 5, including a first stage 705 for determination of a
transmission analog precoder (W.sub.RF) and a receive analog
combiner (F.sub.RF), a second stage 710 for determination of a
transmission baseband precoder (W.sub.BBS[k]), and a third stage
715 for determination of a receive baseband combiner
(F.sub.BBS[k]).
In this example, the first stage 705 may commence at 720 with the
base station 105-f transmitting a CSI-RS using F.sub.RF=F.sub.RF,1
and F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. At 725, the UE 115-f
may receive the CSI-RS using W.sub.RF=W.sub.RF,1 and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. This may be repeated for
other combinations of p and q, at 730, until a last CSI-RS
transmission at 735 and a corresponding reception at 740. At 745,
the UE 115-f may estimate H.sub.eff[k] for all p and q. In some
examples, the UE 115-f may estimate H.sub.eff[k] to be
W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW for all p and q. Thus, the
base station 105-f may select a p-element from a codebook F.sub.RF,
for example, p=1, and transmit the CSI-RS on a directional beam
corresponding to p=1. Similarly, the UE 115-f may select a
q-element from a codebook W.sub.RF, for example, q=1, and receive
the CSI-RS on a directional beam corresponding to q=1. This is
performed for the combinations PQ, and at 750, the UE 115-f may
determine a best or preferred F.sub.RF,p.sub.best and a
W.sub.RF,q.sub.best, based on the different estimates (e.g., that
maximize MI). At 755, the UE 115-f may report the p.sub.best to the
base station 105-f.
At the second stage 710, since the UE 115-f has received a downlink
reference signal using W.sub.RF=W.sub.RF,q.sub.best, no additional
reference signal is needed from the base station 105-f. At 760, the
UE 115-f may determine F.sub.BBS[k] based on H.sub.eff[k] with
respect to the determined p.sub.best and q.sub.best.
At the third stage 715, the UE 115-f may transmit, at 765, a PUSCH
transmission using W.sub.RF,q.sub.best, W.sub.BBS[k], and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. At 770, the base station
105-f may receive the PUSCH using F.sub.RF,p.sub.best,
F.sub.BBS[k], and F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. At 775,
the base station 105-f may estimate H.sub.eff[k] based on the DMRS
(i.e., W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW). At 780, the base
station 105-f may determine F.sub.BBS[k] based on H.sub.eff[k]. At
775, the base station 105-f may decode the PUSCH using F.sub.BBS[k]
at the receive combiner.
FIG. 8 illustrates an example of a process flow 800 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The process flow
800 may illustrate a beam training technique and sequential
approach for determining MIMO beamforming parameters for two or
more beams using a number of downlink reference signals, and an
uplink reference signal. In some examples, the process flow 800 may
implement aspects of the wireless communications systems 100
through 500, as described with reference to FIGS. 1 through 5. For
example, the process flow 800 may be based on a configuration by a
base station 105 or a UE 115, and implemented for reduced power
consumption, spectral efficiency, higher data rates and, in some
examples, may promote high reliability and low latency for
beamforming operations, among other benefits.
The process flow 800 may include a base station 105-g and a UE
115-g, which may be examples of base stations 105 and UEs 115 as
described with reference to FIGS. 1 through 5. In the following
description of the process flow 800, the operations between the
base station 105-g and the UE 115-g may be transmitted in a
different order than the example order shown, or the operations
performed by the base station 105-g and the UE 115-g may be
performed in different orders or at different times. Some
operations may also be omitted from the process flow 800, and other
operations may be added to the process flow 800.
In this example, the process flow 800 includes multiple stages for
downlink MIMO transmissions, in accordance with the discussion of
FIG. 5, including a first stage 805 for determination of a
transmission analog precoder (F.sub.RF) and a receive analog
combiner (W.sub.RF), a second stage 810 for determination of a
transmission baseband precoder (F.sub.BBS[k]), and a third stage
815 for determination of a receive baseband combiner
(W.sub.BBS[k]).
In this example, the first stage 805 may commence at 820 with the
UE 115-g transmitting a SRS using W.sub.RF=W.sub.RF,1 and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. At 825, the base station
105-g may receive the SRS using F.sub.RF=F.sub.RF,1 and
F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. This may be repeated for
other combinations of p and q, at 830, until a last SRS
transmission at 835 and a corresponding reception at 840. At 845,
the base station 105-g may estimate H.sub.eff[k] for all p and q.
In some examples, the UE 115-g may estimate H.sub.eff[k] to be
W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW for all p and q. Thus, the
UE 115-g may select a q-element from a codebook W.sub.RF, for
example, q=1, and transmit the SRS on a directional beam
corresponding to q=1. Similarly, the base station 105-g may select
a p-element from a codebook F.sub.RF, for example, p=1, and receive
the SRS on a directional beam corresponding to p=1. This is
performed for the combinations PQ, and at 850, the base station
105-g may determine a best or preferred F.sub.RF,p.sub.best and a
W.sub.RF,q.sub.best, based on the different estimates (e.g., that
maximize MI). At 855, the base station 105-g may report the
q.sub.best to the UE 115-g.
At the second stage 810, since the base station 105-g has received
an uplink reference signal using F.sub.RF=F.sub.RF,p.sub.best, no
additional reference signal is needed from the UE 115-g. At 860,
the base station 105-g may determine F.sub.BBS[k] based on
H.sub.eff[k] with respect to the determined p.sub.best and
q.sub.best.
At the third stage 815, the base station 105-g may transmit, at
865, a PDSCH transmission using F.sub.RF,p.sub.best, F.sub.BBS[k],
and F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. At 870, the UE 115-g
may receive the PDSCH using W.sub.RF,q.sub.best, W.sub.BBS[k], and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. At 875, the UE 115-g may
estimate H.sub.eff[k] based on the DMRS (i.e.,
W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW). At 880, the UE 115-g may
determine W.sub.BBS[k] based on H.sub.eff[k]. At 875, the UE 115-g
may decode the PDSCH using F.sub.BBS[k] at the receive
combiner.
FIG. 9 illustrates an example of a process flow 900 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The process flow
900 may illustrate a beam training technique and sequential
approach for determining MIMO beamforming parameters for two or
more beams using a number of downlink reference signals, and an
uplink reference signal. In some examples, the process flow 900 may
implement aspects of the wireless communications systems 100
through 500, as described with reference to FIGS. 1 through 5. For
example, the process flow 900 may be based on a configuration by a
base station 105 or a UE 115, and implemented for reduced power
consumption, spectral efficiency, higher data rates and, in some
examples, may promote high reliability and low latency for
beamforming operations, among other benefits.
The process flow 900 may include a base station 105-h and a UE
115-h, which may be examples of base stations 105 and UEs 115 as
described with reference to FIGS. 1 through 5. In the following
description of the process flow 900, the operations between the
base station 105-h and the UE 115-h may be transmitted in a
different order than the example order shown, or the operations
performed by the base station 105-h and the UE 115-h may be
performed in different orders or at different times. Some
operations may also be omitted from the process flow 900, and other
operations may be added to the process flow 900.
In this example, the process flow 900 includes multiple stages for
uplink MIMO transmissions, in accordance with the discussion of
FIG. 5, including a first stage 905 for determination of a
transmission analog precoder (W.sub.RF) and a receive analog
combiner (F.sub.RF), a second stage 910 for determination of a
transmission baseband precoder (W.sub.BBS[k]), and a third stage
915 for determination of a receive baseband combiner
(F.sub.BBS[k]).
In this example, the first stage 905 may commence at 920 with the
UE 115-h transmitting a SRS using W.sub.RF=W.sub.RF,1 and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. At 925, the base station
105-h may receive the SRS using F.sub.RF=F.sub.RF,1 and
F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. This may be repeated for
other combinations of p and q, at 930, until a last SRS
transmission at 935 and a corresponding reception at 940. At 945,
the base station 105-h may estimate H.sub.eff[k] for all p and q.
In some examples, the UE 115-h may estimate H.sub.eff[k] to be
W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW for all p and q. Thus, the
UE 115-h may select a q-element from a codebook W.sub.RF, for
example, q=1, and transmit the SRS on a directional beam
corresponding to q=1. Similarly, the base station 105-h may select
a p-element from a codebook F.sub.RF, for example, p=1, and receive
the SRS on a directional beam corresponding to p=1. This is
performed for the combinations PQ, and at 950, the base station
105-h may determine a best or preferred F.sub.RF,p.sub.best and a
W.sub.RF,q.sub.best, based on the different estimates (e.g., that
maximize MI). At 955, the base station 105-h may report the
q.sub.best to the UE 115-h.
At the second stage 910, the baseband precoder for UE 115-h is
determined. In this example, at 960, the base station 105-h may
transmit a CSI-RS using F.sub.RF=F.sub.RF,q.sub.best and
F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. The UE 115-h, at 965, may
receive the CSI-RS and at 970 estimate H.sub.eff[k] to be
W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW. At 975, the UE 115-h may
determine W.sub.BBS[k] based on H.sub.eff[k].
At the third stage 915, the UE 115-h may transmit, at 980, a PUSCH
transmission using W.sub.RF,q.sub.best, W.sub.BBS[k], and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. At 985, the base station
105-h may receive the PUSCH using F.sub.RF,p.sub.best,
F.sub.BBS[k], and F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. At 990,
the base station 105-h may estimate H.sub.eff[k] based on the DMRS
(i.e., W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW). At 995, the base
station 105-h may determine F.sub.BBS[k] based on H.sub.eff[k]. At
997, the base station 105-h may decode the PUSCH using F.sub.BBS[k]
at the receive combiner.
While the examples of FIGS. 6 through 9 describe transmitting a
reference signal for determination of the baseband precoder at the
second stage in cases where the beam sweeping reference signals are
transmitted by the device that is determining the baseband precoder
(e.g., in the examples of FIGS. 6 and 9). In other cases rather
than transmitting a different reference signal, such as the SRS if
FIG. 6 and the CSI-RS in FIG. 9, a codebook-based report may be
transmitted instead, such as a precoding matrix indicator (PMI),
which may indicate the baseband precoder to be used. Examples of
such codebook-based reports are illustrated in FIGS. 10 and 11.
FIG. 10 illustrates an example of a process flow 1000 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The process flow
1000 may illustrate a beam training technique and sequential
approach for determining MIMO beamforming parameters for two or
more beams using a number of downlink reference signals, and an
uplink reference signal. In some examples, the process flow 1000
may implement aspects of the wireless communications systems 100
through 500, as described with reference to FIGS. 1 through 5. For
example, the process flow 1000 may be based on a configuration by a
base station 105 or a UE 115, and implemented for reduced power
consumption, spectral efficiency, higher data rates and, in some
examples, may promote high reliability and low latency for
beamforming operations, among other benefits.
The process flow 1000 may include a base station 105-j and a UE
115-j, which may be examples of base stations 105 and UEs 115 as
described with reference to FIGS. 1 through 5. In the following
description of the process flow 1000, the operations between the
base station 105-i and the UE 115-i may be transmitted in a
different order than the example order shown, or the operations
performed by the base station 105-i and the UE 115-i may be
performed in different orders or at different times. Some
operations may also be omitted from the process flow 1000, and
other operations may be added to the process flow 1000.
In this example, the process flow 1000 includes multiple stages, in
accordance with the discussion of FIG. 5, including a first stage
1005 for determination of a transmission analog precoder (F.sub.RF)
and a receive analog combiner (W.sub.RF), a second stage 1010 for
determination of a transmission baseband precoder (F.sub.BBS[k]),
and a third stage 1015 for determination of a receive baseband
combiner (W.sub.BBS[k]).
In this example, the first stage 1005, the process flow 1000 may
commence at 1020 with the base station 105-j transmitting a CSI-RS
using F.sub.RF=F.sub.RF,1 and
F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. At 1025, the UE 115-i may
receive the CSI-RS using W.sub.RF=W.sub.RF,1 and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. This may be repeated for
other combinations of p and q, at 1030, until a last CSI-RS
transmission at 1035 and a corresponding reception at 1040. At
1045, the UE 115-i may estimate H.sub.eff[k] for all p and q. In
some examples, the UE 115-i may estimate H.sub.eff[k] to be
W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW for all p and q. Thus, the
base station 105-j may select a p-element from a codebook F.sub.RF,
for example, p=1, and transmit the CSI-RS on a directional beam
corresponding to p=1. Similarly, the UE 115-j may select a
q-element from a codebook W.sub.RF, for example, q=1, and receive
the CSI-RS on a directional beam corresponding to q=1. This is
performed for the combinations PQ, and at 1050, the UE 115-i may
determine a best or preferred F.sub.RF,p.sub.best and a
W.sub.RF,q.sub.best, based on the different estimates (e.g., that
maximize MI). At 1055, the UE 115-i may report the p.sub.best to
the base station 105-i.
At the second stage 1010, the baseband precoder is determined. In
this example, at 1060, the UE 115-i may determine F.sub.BBS[k]
based on H.sub.eff[k] with respect to p.sub.best and q.sub.best. At
1057, the UE 115-i may transmit a report with F.sub.BBS[k]'s, which
in some case may include a PMI for each determined F.sub.BBS[k]
according to a PMI codebook. In some cases, the reports transmitted
at 1055 and 1057 may be combined into a single report that is
provided to the base station 105-i.
At the third stage 1015, the base station 105-i may transmit, at
1065, a PDSCH transmission using F.sub.RF,p.sub.best, F.sub.BBS[k],
and F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2 (e.g. based on the
codebook for PMI). At 1070, the UE 115-i may receive the PDSCH
using W.sub.RF,q.sub.best, W.sub.BBS[k], and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. At 1075, the UE 115-i may
estimate H.sub.eff[k] based on the DMRS (i.e.,
W*.sub.BBWW*.sub.RFHH[K]F.sub.RFF.sub.BBW). At 1080, the UE 115-i
may determine W.sub.BBS[k] based on H.sub.eff[k]. At 1085, the UE
115-i may decode the PDSCH using W.sub.BBS[k] at the receive
combiner.
FIG. 11 illustrates an example of a process flow 1100 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The process flow
1100 may illustrate a beam training technique and sequential
approach for determining MIMO beamforming parameters for two or
more beams using a number of downlink reference signals, and an
uplink reference signal. In some examples, the process flow 1100
may implement aspects of the wireless communications systems 100
through 500, as described with reference to FIGS. 1 through 5. For
example, the process flow 1100 may be based on a configuration by a
base station 105 or a UE 115, and implemented for reduced power
consumption, spectral efficiency, higher data rates and, in some
examples, may promote high reliability and low latency for
beamforming operations, among other benefits.
The process flow 1100 may include a base station 105-j and a UE
115-j, which may be examples of base stations 105 and UEs 115 as
described with reference to FIGS. 1 through 5. In the following
description of the process flow 1100, the operations between the
base station 105-j and the UE 115-j may be transmitted in a
different order than the example order shown, or the operations
performed by the base station 105-j and the UE 115-j may be
performed in different orders or at different times. Some
operations may also be omitted from the process flow 1100, and
other operations may be added to the process flow 1100.
In this example, the process flow 1100 includes multiple stages for
uplink MIMO transmissions, in accordance with the discussion of
FIG. 5, including a first stage 1105 for determination of a
transmission analog precoder (W.sub.RF) and a receive analog
combiner (F.sub.RF), a second stage 1110 for determination of a
transmission baseband precoder (W.sub.BBS[k]), and a third stage
1115 for determination of a receive baseband combiner
(F.sub.BBS[k]).
In this example, the first stage 1105 may commence at 1120 with the
UE 115-j transmitting a SRS using W.sub.RF=W.sub.RF,1 and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. At 1125, the base station
105-j may receive the SRS using F.sub.RF=F.sub.RF,1 and
F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. This may be repeated for
other combinations of p and q, at 1130, until a last SRS
transmission at 1135 and a corresponding reception at 1140. At
1145, the base station 105-j may estimate H.sub.eff[k] for all p
and q. In some examples, the UE 115-j may estimate H.sub.eff[k] to
be W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW for all p and q. Thus,
the UE 115-j may select a q-element from a codebook W.sub.RF, for
example, q=1, and transmit the SRS on a directional beam
corresponding to q=1. Similarly, the base station 105-j may select
a p-element from a codebook F.sub.RF, for example, p=1, and receive
the SRS on a directional beam corresponding to p=1. This is
performed for the combinations PQ, and at 1150, the base station
105-j may determine a best or preferred F.sub.RF,p.sub.best and a
W.sub.RF,q.sub.best, based on the different estimates (e.g., that
maximize MI). At 1155, the base station 105-j may report the
q.sub.best to the UE 115-j.
At the second stage 1110, the baseband precoder for UE 115-j is
determined. In this example, at 1160, the base station 105-j may
determine W.sub.BBS[k] based on H.sub.eff[k] with respect to
p.sub.best and q.sub.best. At 1157, the base station 105-j may
transmit a report with W.sub.BBS[k]'s, which in some case may
include a PMI for each determined W.sub.BBS[k] according to a PMI
codebook. In some cases, the reports transmitted at 1155 and 1157
may be combined into a single report that is provided to the UE
115-j.
At the third stage 1115, the UE 115-j may transmit, at 1165, a
PUSCH transmission using W.sub.RF,q.sub.best, W.sub.BBS[k], and
W.sub.BBW=(W*.sub.RFW.sub.RF).sup.-1/2. At 1170, the base station
105-j may receive the PUSCH using F.sub.RF,p.sub.best,
F.sub.BBS[k], and F.sub.BBW=(F*.sub.RFF.sub.RF).sup.-1/2. At 1175,
the base station 105-j may estimate H.sub.eff[k] based on the DMRS
(i.e., W*.sub.BBWW*.sub.RFH[K]F.sub.RFF.sub.BBW). At 1180, the base
station 105-j may determine F.sub.BBS[k] based on H.sub.eff[k]. At
1185, the base station 105-j may decode the PUSCH using
F.sub.BBS[k] at the receive combiner.
In some cases, the options for which reference signals, or PMI
indications, are provided for determination of baseband precoding
parameters may depend on one or more factors, such as if beam
correspondence is present or not, whether channel reciprocity is
present or not, or combinations thereof. In cases where there
exists beam correspondence with respect to F.sub.RF and W.sub.RF,
then downlink transmission analog RF beams can be used for uplink
reception analog RF beams, and vice versa (at both the base station
and UE). In such cases, the base station may use the uplink receive
analog RF beam for the downlink transmission analog RF beam, and
vice versa. Further, the UE can use the downlink receive analog RF
beam for the uplink transmission analog RF beam, and vice versa. If
there exists channel reciprocity with respect to H[k] (and thus
F.sub.BB[k] and W.sub.BB[k] as well), then the downlink channel
parameters can be used for the uplink channel, and vice versa (at
both the base station and UE). In such cases, the base station may
can determine downlink baseband transmission beams (F.sub.BB[k]) by
using estimated uplink channel (e.g., via SRS). Further the UE can
determine uplink baseband transmission beams (W.sub.BB[k]) by using
estimated downlink channel (e.g., via CSI-RS). Different options
for determining second stage baseband precoding parameters may thus
depend upon whether there is beam correspondence, channel
reciprocity, or both.
FIG. 12 shows a block diagram 1200 of a device 1205 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The device 1205
may be an example of aspects of a UE 115 or base station 105 as
described herein. The device 1205 may include a receiver 1210, a
communications manager 1215, and a transmitter 1220. The device
1205 may also include a processor. Each of these components may be
in communication with one another (e.g., via one or more
buses).
Receiver 1210 may receive information such as packets, user data,
or control information associated with various information channels
(e.g., control channels, data channels, and information related to
multi-beam selection for beamformed MIMO wireless communications,
etc.). Information may be passed on to other components of the
device 1205. The receiver 1210 may be an example of aspects of the
transceiver 1520 or 1620 as described with reference to FIGS. 15
and 16. The receiver 1210 may utilize a single antenna or a set of
antennas.
The communications manager 1215, when present in a wireless device
that transmits reference signals in a beam training sequence, may
transmit, from a first wireless device, a set of reference signals
to a second wireless device using a set of combinations of analog
beamforming parameters associated with two or more beams that are
configured to carry two or more MIMO streams, where the set of
reference signals are transmitted for different combinations of one
or more sets of transmit beamforming parameters and one or more
sets of receive beamforming parameters, receive, from the second
wireless device, a report that indicates a first combination of
analog beamforming parameters is selected for the analog
beamforming parameters at the second wireless device, and
communicate with the second wireless device via the two or more
beams based on the first combination of analog beamforming
parameters.
The communications manager 1215 when present in a wireless device
that receives reference signals in a beam training sequence, may
measure, at a second wireless device, a channel quality of a set of
reference signals that are transmitted by a first wireless device
using a set of combinations of analog beamforming parameters for
two or more beams that carry two or more MIMO streams, where the
set of reference signals are transmitted for different combinations
of one or more sets of transmit beamforming parameters and one or
more sets of receive beamforming parameters, select a first
combination of analog beamforming parameters based on the measured
channel quality of the set of reference signals, and communicate
with the first wireless device via the two or more beams based on
the first combination of analog beamforming parameters.
The communications manager 1215 may also receive, at a first
wireless device, a set of reference signals that are transmitted by
a second wireless device using a set of combinations of analog
beamforming parameters for two or more beams that carry two or more
MIMO streams, determine a set of analog beamforming parameters for
the two or more beams based on measurements of the set of reference
signals, determine a set of transmission baseband precoder
parameters to be applied to baseband signals of the two or more
beams based on a channel estimation of a channel between the first
wireless device and the second wireless device, determine a set of
receive baseband combiner parameters to be applied to baseband
signals of the two or more beams based on the channel estimation,
and communicate with the second wireless device using the two or
more beams based on the set of analog beamforming parameters, the
set of transmission baseband precoder parameters, and the set of
receive baseband combiner parameters. The communications manager
1215 may be an example of aspects of the communications manager
1510 or 1610 as described herein.
The communications manager 1215, or its sub-components, may be
implemented in hardware, code (e.g., software or firmware) executed
by a processor, or any combination thereof. If implemented in code
executed by a processor, the functions of the communications
manager 1215, or its sub-components may be executed by a
general-purpose processor, a DSP, an application-specific
integrated circuit (ASIC), a FPGA or other programmable logic
device, discrete gate or transistor logic, discrete hardware
components, or any combination thereof designed to perform the
functions described in the present disclosure.
The communications manager 1215, or its sub-components, may be
physically located at various positions, including being
distributed such that portions of functions are implemented at
different physical locations by one or more physical components. In
some examples, the communications manager 1215, or its
sub-components, may be a separate and distinct component in
accordance with various aspects of the present disclosure. In some
examples, the communications manager 1215, or its sub-components,
may be combined with one or more other hardware components,
including but not limited to an input/output (I/O) component, a
transceiver, a network server, another computing device, one or
more other components described in the present disclosure, or a
combination thereof in accordance with various aspects of the
present disclosure.
Transmitter 1220 may transmit signals generated by other components
of the device 1205. In some examples, the transmitter 1220 may be
collocated with a receiver 1210 in a transceiver module. For
example, the transmitter 1220 may be an example of aspects of the
transceiver 1520 or 1620 as described with reference to FIGS. 15
and 16. The transmitter 1220 may utilize a single antenna or a set
of antennas.
FIG. 13 shows a block diagram 1300 of a device 1305 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The device 1305
may be an example of aspects of a device 1205, a UE 115, or a base
station 105 as described herein. The device 1305 may include a
receiver 1310, a communications manager 1315, and a transmitter
1345. The device 1305 may also include a processor. Each of these
components may be in communication with one another (e.g., via one
or more buses).
Receiver 1310 may receive information such as packets, user data,
or control information associated with various information channels
(e.g., control channels, data channels, and information related to
multi-beam selection for beamformed MIMO wireless communications,
etc.). Information may be passed on to other components of the
device 1305. The receiver 1310 may be an example of aspects of the
transceiver 1520 or 1620 as described with reference to FIGS. 15
and 16. The receiver 1310 may utilize a single antenna or a set of
antennas.
The communications manager 1315 may be an example of aspects of the
communications manager 1215 as described herein. The communications
manager 1315 may include a reference signal manager 1320, a
wideband parameter manager 1325, a MIMO manager 1330, a precoding
parameter manager 1335, and a combiner parameter manager 1340. The
communications manager 1315 may be an example of aspects of the
communications manager 1510 or 1610 as described herein.
In some cases, the reference signal manager 1320 may transmit, from
a first wireless device, a set of reference signals to a second
wireless device using a set of combinations of analog beamforming
parameters associated with two or more beams that are configured to
carry two or more MIMO streams, where the set of reference signals
are transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters. The wideband parameter manager 1325 may
receive, from the second wireless device, a report that indicates a
first combination of analog beamforming parameters is selected for
the analog beamforming parameters at the second wireless device.
The MIMO manager 1330 may communicate with the second wireless
device via the two or more beams based on the first combination of
analog beamforming parameters.
In some cases, the reference signal manager 1320 may measure, at a
second wireless device, a channel quality of a set of reference
signals that are transmitted by a first wireless device using a set
of combinations of analog beamforming parameters for two or more
beams that carry two or more MIMO streams, where the set of
reference signals are transmitted for different combinations of one
or more sets of transmit beamforming parameters and one or more
sets of receive beamforming parameters. The wideband parameter
manager 1325 may select a first combination of analog beamforming
parameters based on the measured channel quality of the set of
reference signals. The MIMO manager 1330 may communicate with the
first wireless device via the two or more beams based on the first
combination of analog beamforming parameters.
In some cases, the reference signal manager 1320 may receive, at a
first wireless device, a set of reference signals that are
transmitted by a second wireless device using a set of combinations
of analog beamforming parameters for two or more beams that carry
two or more MIMO streams. The wideband parameter manager 1325 may
determine a set of analog beamforming parameters for the two or
more beams based on measurements of the set of reference signals.
The precoding parameter manager 1335 may determine a set of
transmission baseband precoder parameters to be applied to baseband
signals of the two or more beams based on a channel estimation of a
channel between the first wireless device and the second wireless
device. The combiner parameter manager 1340 may determine a set of
receive baseband combiner parameters to be applied to baseband
signals of the two or more beams based on the channel estimation.
The MIMO manager 1330 may communicate with the second wireless
device using the two or more beams based on the set of analog
beamforming parameters, the set of transmission baseband precoder
parameters, and the set of receive baseband combiner
parameters.
Transmitter 1345 may transmit signals generated by other components
of the device 1305. In some examples, the transmitter 1345 may be
collocated with a receiver 1310 in a transceiver module. For
example, the transmitter 1345 may be an example of aspects of the
transceiver 1520 or 1620 as described with reference to FIGS. 15
and 16. The transmitter 1345 may utilize a single antenna or a set
of antennas.
FIG. 14 shows a block diagram 1400 of a communications manager 1405
that supports multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure. The communications manager 1405 may be an example of
aspects of a communications manager 1215, a communications manager
1315, or a communications manager 1510 described herein. The
communications manager 1405 may include a reference signal manager
1410, a wideband parameter manager 1415, a MIMO manager 1420, a
channel estimation component 1425, a precoding parameter manager
1430, a combiner parameter manager 1435, and a codebook manager
1440. Each of these modules may communicate, directly or
indirectly, with one another (e.g., via one or more buses).
The reference signal manager 1410 may transmit, from a first
wireless device, a set of reference signals to a second wireless
device using a set of combinations of analog beamforming parameters
associated with two or more beams that are configured to carry two
or more MIMO streams, where the set of reference signals are
transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters.
In some examples, the reference signal manager 1410 may measure, at
a second wireless device, a channel quality of a set of reference
signals that are transmitted by a first wireless device using a set
of combinations of analog beamforming parameters for two or more
beams that carry two or more MIMO streams, where the set of
reference signals are transmitted for different combinations of one
or more sets of transmit beamforming parameters and one or more
sets of receive beamforming parameters.
In some examples, the reference signal manager 1410 may receive, at
a first wireless device, a set of reference signals that are
transmitted by a second wireless device using a set of combinations
of analog beamforming parameters for two or more beams that carry
two or more MIMO streams. In some examples, the reference signal
manager 1410 may receive, from the second wireless device, a second
reference signal that is transmitted using the first combination of
analog beamforming parameters.
In some examples, the reference signal manager 1410 may transmit a
second reference signal to the first wireless device using the
first combination of analog beamforming parameters for
determination of a set of transmission baseband precoder parameters
at the first wireless device.
In some cases, the first wireless device is a UE and the second
wireless device is a base station, and where the set of reference
signals are downlink reference signals transmitted to the UE in a
beam sweeping procedure. In some cases, the downlink reference
signals include one or more of a channel state information
reference signal (CSI-RS), one or more reference signals
transmitted in a synchronization signal block (SSB), or any
combinations thereof.
In some cases, the first wireless device is a base station and the
second wireless device is a UE, and where the set of reference
signals are uplink reference signals transmitted to the base
station in a beam sweeping procedure. In some cases, the uplink
reference signals include sounding reference signals (SRS).
In some cases, the set of reference signals include reference
signals that are specific to transmissions from the first wireless
device to the second wireless device, and where the first wireless
device determines a second combination of analog beamforming
parameters for use at the first wireless device based on one or
more different reference signals that are specific to transmissions
from the second wireless device to the first wireless device.
In some cases, the data communications include a third reference
signal for determination of a set of receive baseband combiner
parameters to be applied to baseband signals of the two or more
beams at the second wireless device. In some cases, the third
reference signal is a demodulation reference signal (DMRS).
In some cases, the set of reference signals include reference
signals that are specific to transmissions from the second wireless
device to the first wireless device, and where the second wireless
device determines a second combination of analog beamforming
parameters for use at the second wireless device based on one or
more different reference signals that are specific to transmissions
from the second wireless device to the first wireless device.
The wideband parameter manager 1415 may receive, from the second
wireless device, a report that indicates a first combination of
analog beamforming parameters is selected for the analog
beamforming parameters at the second wireless device.
In some examples, the wideband parameter manager 1415 may select a
first combination of analog beamforming parameters based on the
measured channel quality of the set of reference signals.
In some examples, the wideband parameter manager 1415 may determine
a set of analog beamforming parameters for the two or more beams
based on measurements of the set of reference signals.
In some cases, the analog beamforming parameters are used to
transform signals received at a set of antennas to baseband signals
that are provided to a set of radio frequency receive chains. In
some cases, the analog beamforming parameters are used to transform
the baseband signals received at the radio frequency transmit
chains into radio frequency signals for transmission from a set of
antennas.
The MIMO manager 1420 may communicate with the second wireless
device via the two or more beams based on the first combination of
analog beamforming parameters.
In some examples, the MIMO manager 1420 may communicate with the
first wireless device via the two or more beams based on the first
combination of analog beamforming parameters.
In some examples, the MIMO manager 1420 may communicate with the
second wireless device using the two or more beams based on the set
of analog beamforming parameters, the set of transmission baseband
precoder parameters, and the set of receive baseband combiner
parameters.
In some examples, the MIMO manager 1420 may transmit a data
transmission and a third reference signal to the second wireless
device via the two or more MIMO streams on the two or more beams,
and where the second wireless device determines a set of receive
baseband combiner parameters to be applied to baseband signals of
received transmissions using the two or more beams based on the
third reference signal.
In some examples, the MIMO manager 1420 may receive a data
transmission and a third reference signal from the first wireless
device via the two or more MIMO streams on the two or more beams.
In some examples, the MIMO manager 1420 may decode the data
transmission using the receive baseband combiner parameters.
In some cases, the communicating with the second wireless device
includes data communications via the two or more MIMO streams on
the two or more beams, where the two or more beams use the first
combination of analog beamforming parameters and the set of
transmission baseband precoder parameters.
In some cases, the first wireless device determines a set of
transmission baseband precoder parameters to be applied to baseband
signals for transmissions using the two or more beams based on a
second reference signal received from the second wireless device,
where the baseband precoder parameters are used to transform input
from the two or more MIMO streams into baseband streams of a set of
radio frequency transmit chains, and where the first combination of
analog beamforming parameters are used to transform the baseband
streams of the set of radio frequency transmit chains into wideband
waveforms that are provided to a set of antennas.
The precoding parameter manager 1430 may determine a set of
transmission baseband precoder parameters to be applied to baseband
signals of the two or more beams based on a channel estimation of a
channel between the first wireless device and the second wireless
device.
In some examples, the precoding parameter manager 1430 may
determine a set of transmission baseband precoder parameters to be
applied to baseband signals of the two or more beams based on the
estimating the effective channel.
In some examples, the precoding parameter manager 1430 may receive
an indication from the second wireless device of a set of
transmission baseband precoder parameters to be applied to baseband
signals for transmissions from the first wireless device using the
two or more beams.
In some examples, the precoding parameter manager 1430 may
determine a set of transmission baseband precoder parameters to be
applied to baseband signals for transmissions from the second
wireless device using the two or more beams based on the set of
reference signals transmitted by the first wireless device.
In some examples, the precoding parameter manager 1430 may transmit
a second reference signal to the first wireless device using the
first combination of analog beamforming parameters for
determination of a set of transmission baseband precoder parameters
to be applied to baseband signals for transmissions from the first
wireless device using the two or more beams.
In some examples, the precoding parameter manager 1430 may transmit
an indication to the first wireless device of a set of transmission
baseband precoder parameters to be applied to baseband signals for
transmissions from the first wireless device using the two or more
beams.
In some cases, the second wireless device determines a set of
transmission baseband precoder parameters to be applied to baseband
signals for transmissions from the second wireless device using the
two or more beams based on the set of reference signals transmitted
by the first wireless device. In some cases, the indication from
the second wireless device is a precoding matrix indicator (PMI)
that is mapped to a codebook of sets of transmission baseband
precoder parameters. In some cases, the baseband precoder
parameters are used to transform the two or more MIMO streams into
baseband signals that are provided to a set of radio frequency
transmit chains.
The combiner parameter manager 1435 may determine a set of receive
baseband combiner parameters to be applied to baseband signals of
the two or more beams based on the channel estimation.
In some examples, the combiner parameter manager 1435 may
determine, based on measurements of the third reference signal, a
set of receive baseband combiner parameters to be applied to
baseband signals of received transmissions using the two or more
beams.
In some cases, the data communications include a third reference
signal for measurement at the second wireless device and
determination of a set of receive baseband combiner parameters to
be applied to baseband signals of the two or more beams at the
second wireless device. In some cases, the baseband combiner
parameters are used to transform an output of the set of radio
frequency receive chains into the two or more MIMO streams.
The channel estimation component 1425 may estimate an effective
channel between the first wireless device and the second wireless
device based on one or more measurements of the second reference
signal.
In some examples, the channel estimation component 1425 may
estimate an effective channel between the second wireless device
and the first wireless device for each of the different
combinations of the one or more sets of transmit beamforming
parameters and the one or more sets of receive beamforming
parameters, and where the first combination of analog beamforming
parameters is selected based on a magnitude of the effective
channel estimates.
In some examples, the channel estimation component 1425 may
estimate an effective channel between the second wireless device
and the first wireless device based on measurements of the third
reference signal. In some examples, the channel estimation
component 1425 may determine the set of receive baseband combiner
parameters based on the estimating.
The codebook manager 1440 may transmit a report that indicates the
first combination of analog beamforming parameters is selected for
the analog beamforming parameters, and where the report indicates a
codebook index value for a codebook of beamforming parameters, and
where the codebook of beamforming parameters maps codebook index
values to the different combinations of the one or more sets of
transmit beamforming parameters and the one or more sets of receive
beamforming parameters.
In some cases, the first combination of analog beamforming
parameters is associated with a first reference signal transmission
that has a highest mutual information (MI) value of the set of
reference signals.
FIG. 15 shows a diagram of a system 1500 including a device 1505
that supports multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure. The device 1505 may be an example of or include the
components of device 1205, device 1305, or a UE 115 as described
herein. The device 1505 may include components for bi-directional
voice and data communications including components for transmitting
and receiving communications, including a communications manager
1510, a transceiver 1520, an antenna 1525, memory 1530, a processor
1540, and an I/O controller 1550. These components may be in
electronic communication via one or more buses (e.g., bus
1555).
The communications manager 1510 may transmit, from a first wireless
device, a set of reference signals to a second wireless device
using a set of combinations of analog beamforming parameters
associated with two or more beams that are configured to carry two
or more MIMO streams, where the set of reference signals are
transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters, receive, from the second wireless device, a
report that indicates a first combination of analog beamforming
parameters is selected for the analog beamforming parameters at the
second wireless device, and communicate with the second wireless
device via the two or more beams based on the first combination of
analog beamforming parameters.
The communications manager 1510 may also measure, at a second
wireless device, a channel quality of a set of reference signals
that are transmitted by a first wireless device using a set of
combinations of analog beamforming parameters for two or more beams
that carry two or more MIMO streams, where the set of reference
signals are transmitted for different combinations of one or more
sets of transmit beamforming parameters and one or more sets of
receive beamforming parameters, select a first combination of
analog beamforming parameters based on the measured channel quality
of the set of reference signals, and communicate with the first
wireless device via the two or more beams based on the first
combination of analog beamforming parameters.
The communications manager 1510 may also receive, at a first
wireless device, a set of reference signals that are transmitted by
a second wireless device using a set of combinations of analog
beamforming parameters for two or more beams that carry two or more
MIMO streams, determine a set of analog beamforming parameters for
the two or more beams based on measurements of the set of reference
signals, determine a set of transmission baseband precoder
parameters to be applied to baseband signals of the two or more
beams based on a channel estimation of a channel between the first
wireless device and the second wireless device, determine a set of
receive baseband combiner parameters to be applied to baseband
signals of the two or more beams based on the channel estimation,
and communicate with the second wireless device using the two or
more beams based on the set of analog beamforming parameters, the
set of transmission baseband precoder parameters, and the set of
receive baseband combiner parameters.
Transceiver 1520 may communicate bi-directionally, via one or more
antennas, wired, or wireless links as described above. For example,
the transceiver 1520 may represent a wireless transceiver and may
communicate bi-directionally with another wireless transceiver. The
transceiver 1520 may also include a modem to modulate the packets
and provide the modulated packets to the antennas for transmission,
and to demodulate packets received from the antennas.
In some cases, the wireless device may include a single antenna
1525. However, in some cases the device may have more than one
antenna 1525, which may be capable of concurrently transmitting or
receiving multiple wireless transmissions.
The memory 1530 may include RAM, ROM, or a combination thereof. The
memory 1530 may store computer-readable code 1535 including
instructions that, when executed by a processor (e.g., the
processor 1540) cause the device to perform various functions
described herein. In some cases, the memory 1530 may contain, among
other things, a BIOS which may control basic hardware or software
operation such as the interaction with peripheral components or
devices.
The processor 1540 may include an intelligent hardware device,
(e.g., a general-purpose processor, a DSP, a CPU, a
microcontroller, an ASIC, an FPGA, a programmable logic device, a
discrete gate or transistor logic component, a discrete hardware
component, or any combination thereof). In some cases, the
processor 1540 may be configured to operate a memory array using a
memory controller. In other cases, a memory controller may be
integrated into the processor 1540. The processor 1540 may be
configured to execute computer-readable instructions stored in a
memory (e.g., the memory 1530) to cause the device 1505 to perform
various functions (e.g., functions or tasks supporting multi-beam
selection for beamformed MIMO wireless communications).
The I/O controller 1550 may manage input and output signals for the
device 1505. The I/O controller 1550 may also manage peripherals
not integrated into the device 1505. In some cases, the I/O
controller 1550 may represent a physical connection or port to an
external peripheral. In some cases, the I/O controller 1550 may
utilize an operating system such as iOS.RTM., ANDROID.RTM.,
MS-DOS.RTM., MS-WINDOWS.RTM., OS/2.RTM., UNIX.RTM., LINUX.RTM., or
another known operating system. In other cases, the I/O controller
1550 may represent or interact with a modem, a keyboard, a mouse, a
touchscreen, or a similar device. In some cases, the I/O controller
1550 may be implemented as part of a processor. In some cases, a
user may interact with the device 1505 via the I/O controller 1550
or via hardware components controlled by the I/O controller
1550.
The code 1535 may include instructions to implement aspects of the
present disclosure, including instructions to support wireless
communications. The code 1535 may be stored in a non-transitory
computer-readable medium such as system memory or other type of
memory. In some cases, the code 1535 may not be directly executable
by the processor 1540 but may cause a computer (e.g., when compiled
and executed) to perform functions described herein.
FIG. 16 shows a diagram of a system 1600 including a device 1605
that supports multi-beam selection for beamformed MIMO wireless
communications in accordance with aspects of the present
disclosure. The device 1605 may be an example of or include the
components of device 1205, device 1305, or a base station 105 as
described herein. The device 1605 may include components for
bi-directional voice and data communications including components
for transmitting and receiving communications, including a
communications manager 1610, a network communications manager 1615,
a transceiver 1620, an antenna 1625, memory 1630, a processor 1640,
and an inter-station communications manager 1645. These components
may be in electronic communication via one or more buses (e.g., bus
1655).
The communications manager 1610 may transmit, from a first wireless
device, a set of reference signals to a second wireless device
using a set of combinations of analog beamforming parameters
associated with two or more beams that are configured to carry two
or more MIMO streams, where the set of reference signals are
transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters, receive, from the second wireless device, a
report that indicates a first combination of analog beamforming
parameters is selected for the analog beamforming parameters at the
second wireless device, and communicate with the second wireless
device via the two or more beams based on the first combination of
analog beamforming parameters.
The communications manager 1610 may also measure, at a second
wireless device, a channel quality of a set of reference signals
that are transmitted by a first wireless device using a set of
combinations of analog beamforming parameters for two or more beams
that carry two or more MIMO streams, where the set of reference
signals are transmitted for different combinations of one or more
sets of transmit beamforming parameters and one or more sets of
receive beamforming parameters, select a first combination of
analog beamforming parameters based on the measured channel quality
of the set of reference signals, and communicate with the first
wireless device via the two or more beams based on the first
combination of analog beamforming parameters.
The communications manager 1610 may also receive, at a first
wireless device, a set of reference signals that are transmitted by
a second wireless device using a set of combinations of analog
beamforming parameters for two or more beams that carry two or more
MIMO streams, determine a set of analog beamforming parameters for
the two or more beams based on measurements of the set of reference
signals, determine a set of transmission baseband precoder
parameters to be applied to baseband signals of the two or more
beams based on a channel estimation of a channel between the first
wireless device and the second wireless device, determine a set of
receive baseband combiner parameters to be applied to baseband
signals of the two or more beams based on the channel estimation,
and communicate with the second wireless device using the two or
more beams based on the set of analog beamforming parameters, the
set of transmission baseband precoder parameters, and the set of
receive baseband combiner parameters.
Network communications manager 1615 may manage communications with
the core network (e.g., via one or more wired backhaul links). For
example, the network communications manager 1615 may manage the
transfer of data communications for client devices, such as one or
more UEs 115.
Transceiver 1620 may communicate bi-directionally, via one or more
antennas, wired, or wireless links as described above. For example,
the transceiver 1620 may represent a wireless transceiver and may
communicate bi-directionally with another wireless transceiver. The
transceiver 1620 may also include a modem to modulate the packets
and provide the modulated packets to the antennas for transmission,
and to demodulate packets received from the antennas.
In some cases, the wireless device may include a single antenna
1625. However, in some cases the device may have more than one
antenna 1625, which may be capable of concurrently transmitting or
receiving multiple wireless transmissions.
The memory 1630 may include RAM, ROM, or a combination thereof. The
memory 1630 may store computer-readable code 1635 including
instructions that, when executed by a processor (e.g., the
processor 1640) cause the device to perform various functions
described herein. In some cases, the memory 1630 may contain, among
other things, a BIOS which may control basic hardware or software
operation such as the interaction with peripheral components or
devices.
The processor 1640 may include an intelligent hardware device,
(e.g., a general-purpose processor, a DSP, a CPU, a
microcontroller, an ASIC, an FPGA, a programmable logic device, a
discrete gate or transistor logic component, a discrete hardware
component, or any combination thereof). In some cases, the
processor 1640 may be configured to operate a memory array using a
memory controller. In other cases, a memory controller may be
integrated into the processor 1640. The processor 1640 may be
configured to execute computer-readable instructions stored in a
memory (e.g., the memory 1630) to cause the device 1605 to perform
various functions (e.g., functions or tasks supporting multi-beam
selection for beamformed MIMO wireless communications).
Inter-station communications manager 1645 may manage communications
with other base station 105, and may include a controller or
scheduler for controlling communications with UEs 115 in
cooperation with other base stations 105. For example, the
inter-station communications manager 1645 may coordinate scheduling
for transmissions to UEs 115 for various interference mitigation
techniques such as beamforming or joint transmission. In some
examples, inter-station communications manager 1645 may provide an
X2 interface within an LTE/LTE-A wireless communication network
technology to provide communication between base stations 105.
The code 1635 may include instructions to implement aspects of the
present disclosure, including instructions to support wireless
communications. The code 1635 may be stored in a non-transitory
computer-readable medium such as system memory or other type of
memory. In some cases, the code 1635 may not be directly executable
by the processor 1640 but may cause a computer (e.g., when compiled
and executed) to perform functions described herein.
FIG. 17 shows a flowchart illustrating a method 1700 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The operations
of method 1700 may be implemented by a UE 115 or base station 105
or its components as described herein. For example, the operations
of method 1700 may be performed by a communications manager as
described with reference to FIGS. 12 through 16. In some examples,
a UE or base station may execute a set of instructions to control
the functional elements of the UE or base station to perform the
functions described below. Additionally or alternatively, a UE or
base station may perform aspects of the functions described below
using special-purpose hardware.
At 1705, the UE or base station may transmit, from a first wireless
device, a set of reference signals to a second wireless device
using a set of combinations of analog beamforming parameters
associated with two or more beams that are configured to carry two
or more MIMO streams, where the set of reference signals are
transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters. The operations of 1705 may be performed
according to the methods described herein. In some examples,
aspects of the operations of 1705 may be performed by a reference
signal manager as described with reference to FIGS. 12 through
16.
At 1710, the UE or base station may receive, from the second
wireless device, a report that indicates a first combination of
analog beamforming parameters is selected for the analog
beamforming parameters at the second wireless device. The
operations of 1710 may be performed according to the methods
described herein. In some examples, aspects of the operations of
1710 may be performed by a wideband parameter manager as described
with reference to FIGS. 12 through 16.
At 1715, the UE or base station may communicate with the second
wireless device via the two or more beams based on the first
combination of analog beamforming parameters. The operations of
1715 may be performed according to the methods described herein. In
some examples, aspects of the operations of 1715 may be performed
by a MIMO manager as described with reference to FIGS. 12 through
16.
FIG. 18 shows a flowchart illustrating a method 1800 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The operations
of method 1800 may be implemented by a UE 115 or base station 105
or its components as described herein. For example, the operations
of method 1800 may be performed by a communications manager as
described with reference to FIGS. 12 through 16. In some examples,
a UE or base station may execute a set of instructions to control
the functional elements of the UE or base station to perform the
functions described below. Additionally or alternatively, a UE or
base station may perform aspects of the functions described below
using special-purpose hardware.
At 1805, the UE or base station may transmit, from a first wireless
device, a set of reference signals to a second wireless device
using a set of combinations of analog beamforming parameters
associated with two or more beams that are configured to carry two
or more MIMO streams, where the set of reference signals are
transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters. The operations of 1805 may be performed
according to the methods described herein. In some examples,
aspects of the operations of 1805 may be performed by a reference
signal manager as described with reference to FIGS. 12 through
16.
At 1810, the UE or base station may receive, from the second
wireless device, a report that indicates a first combination of
analog beamforming parameters is selected for the analog
beamforming parameters at the second wireless device. The
operations of 1810 may be performed according to the methods
described herein. In some examples, aspects of the operations of
1810 may be performed by a wideband parameter manager as described
with reference to FIGS. 12 through 16.
At 1815, the UE or base station may receive, from the second
wireless device, a second reference signal that is transmitted
using the first combination of analog beamforming parameters. The
operations of 1815 may be performed according to the methods
described herein. In some examples, aspects of the operations of
1815 may be performed by a reference signal manager as described
with reference to FIGS. 12 through 16.
At 1820, the UE or base station may estimate an effective channel
between the first wireless device and the second wireless device
based on one or more measurements of the second reference signal.
The operations of 1820 may be performed according to the methods
described herein. In some examples, aspects of the operations of
1820 may be performed by a channel estimation component as
described with reference to FIGS. 12 through 16.
At 1825, the UE or base station may determine a set of transmission
baseband precoder parameters to be applied to baseband signals of
the two or more beams based on the estimating the effective
channel. The operations of 1825 may be performed according to the
methods described herein. In some examples, aspects of the
operations of 1825 may be performed by a precoding parameter
manager as described with reference to FIGS. 12 through 16.
At 1830, the UE or base station may communicate with the second
wireless device via the two or more beams based on the first
combination of analog beamforming parameters. The operations of
1830 may be performed according to the methods described herein. In
some examples, aspects of the operations of 1830 may be performed
by a MIMO manager as described with reference to FIGS. 12 through
16. In some cases, the communicating with the second wireless
device includes data communications via the two or more MIMO
streams on the two or more beams, where the two or more beams use
the first combination of analog beamforming parameters and the set
of transmission baseband precoder parameters. In some cases, the
data communications include a third reference signal for
measurement at the second wireless device and determination of a
set of receive baseband combiner parameters to be applied to
baseband signals of the two or more beams at the second wireless
device.
FIG. 19 shows a flowchart illustrating a method 1900 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The operations
of method 1900 may be implemented by a UE 115 or base station 105
or its components as described herein. For example, the operations
of method 1900 may be performed by a communications manager as
described with reference to FIGS. 12 through 16. In some examples,
a UE or base station may execute a set of instructions to control
the functional elements of the UE or base station to perform the
functions described below. Additionally or alternatively, a UE or
base station may perform aspects of the functions described below
using special-purpose hardware.
At 1905, the UE or base station may transmit, from a first wireless
device, a set of reference signals to a second wireless device
using a set of combinations of analog beamforming parameters
associated with two or more beams that are configured to carry two
or more MIMO streams, where the set of reference signals are
transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters. The operations of 1905 may be performed
according to the methods described herein. In some examples,
aspects of the operations of 1905 may be performed by a reference
signal manager as described with reference to FIGS. 12 through
16.
At 1910, the UE or base station may receive, from the second
wireless device, a report that indicates a first combination of
analog beamforming parameters is selected for the analog
beamforming parameters at the second wireless device. The
operations of 1910 may be performed according to the methods
described herein. In some examples, aspects of the operations of
1910 may be performed by a wideband parameter manager as described
with reference to FIGS. 12 through 16.
At 1915, the UE or base station may receive an indication from the
second wireless device of a set of transmission baseband precoder
parameters to be applied to baseband signals for transmissions from
the first wireless device using the two or more beams. The
operations of 1915 may be performed according to the methods
described herein. In some examples, aspects of the operations of
1915 may be performed by a precoding parameter manager as described
with reference to FIGS. 12 through 16. In some cases, the
indication from the second wireless device is a precoding matrix
indicator (PMI) that is mapped to a codebook of sets of
transmission baseband precoder parameters.
At 1920, the UE or base station may communicate with the second
wireless device via the two or more beams based on the first
combination of analog beamforming parameters. The operations of
1920 may be performed according to the methods described herein. In
some examples, aspects of the operations of 1920 may be performed
by a MIMO manager as described with reference to FIGS. 12 through
16.
FIG. 20 shows a flowchart illustrating a method 2000 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The operations
of method 2000 may be implemented by a UE 115 or base station 105
or its components as described herein. For example, the operations
of method 2000 may be performed by a communications manager as
described with reference to FIGS. 12 through 16. In some examples,
a UE or base station may execute a set of instructions to control
the functional elements of the UE or base station to perform the
functions described below. Additionally or alternatively, a UE or
base station may perform aspects of the functions described below
using special-purpose hardware.
At 2005, the UE or base station may transmit, from a first wireless
device, a set of reference signals to a second wireless device
using a set of combinations of analog beamforming parameters
associated with two or more beams that are configured to carry two
or more MIMO streams, where the set of reference signals are
transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters. The operations of 2005 may be performed
according to the methods described herein. In some examples,
aspects of the operations of 2005 may be performed by a reference
signal manager as described with reference to FIGS. 12 through
16.
At 2010, the UE or base station may receive, from the second
wireless device, a report that indicates a first combination of
analog beamforming parameters is selected for the analog
beamforming parameters at the second wireless device. The
operations of 2010 may be performed according to the methods
described herein. In some examples, aspects of the operations of
2010 may be performed by a wideband parameter manager as described
with reference to FIGS. 12 through 16.
At 2015, the UE or base station may communicate with the second
wireless device via the two or more beams based on the first
combination of analog beamforming parameters. The operations of
2015 may be performed according to the methods described herein. In
some examples, aspects of the operations of 2015 may be performed
by a MIMO manager as described with reference to FIGS. 12 through
16.
At 2020, the UE or base station may transmit a data transmission
and a third reference signal to the second wireless device via the
two or more MIMO streams on the two or more beams, and where the
second wireless device determines a set of receive baseband
combiner parameters to be applied to baseband signals of received
transmissions using the two or more beams based on the third
reference signal. The operations of 2020 may be performed according
to the methods described herein. In some examples, aspects of the
operations of 2020 may be performed by a MIMO manager as described
with reference to FIGS. 12 through 16.
FIG. 21 shows a flowchart illustrating a method 2100 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The operations
of method 2100 may be implemented by a UE 115 or base station 105
or its components as described herein. For example, the operations
of method 2100 may be performed by a communications manager as
described with reference to FIGS. 12 through 16. In some examples,
a UE or base station may execute a set of instructions to control
the functional elements of the UE or base station to perform the
functions described below. Additionally or alternatively, a UE or
base station may perform aspects of the functions described below
using special-purpose hardware.
At 2105, the UE or base station may measure, at a second wireless
device, a channel quality of a set of reference signals that are
transmitted by a first wireless device using a set of combinations
of analog beamforming parameters for two or more beams that carry
two or more MIMO streams, where the set of reference signals are
transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters. The operations of 2105 may be performed
according to the methods described herein. In some examples,
aspects of the operations of 2105 may be performed by a reference
signal manager as described with reference to FIGS. 12 through
16.
At 2110, the UE or base station may select a first combination of
analog beamforming parameters based on the measured channel quality
of the set of reference signals. The operations of 2110 may be
performed according to the methods described herein. In some
examples, aspects of the operations of 2110 may be performed by a
wideband parameter manager as described with reference to FIGS. 12
through 16.
At 2115, the UE or base station may communicate with the first
wireless device via the two or more beams based on the first
combination of analog beamforming parameters. The operations of
2115 may be performed according to the methods described herein. In
some examples, aspects of the operations of 2115 may be performed
by a MIMO manager as described with reference to FIGS. 12 through
16.
FIG. 22 shows a flowchart illustrating a method 2200 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The operations
of method 2200 may be implemented by a UE 115 or base station 105
or its components as described herein. For example, the operations
of method 2200 may be performed by a communications manager as
described with reference to FIGS. 12 through 16. In some examples,
a UE or base station may execute a set of instructions to control
the functional elements of the UE or base station to perform the
functions described below. Additionally or alternatively, a UE or
base station may perform aspects of the functions described below
using special-purpose hardware.
At 2205, the UE or base station may measure, at a second wireless
device, a channel quality of a set of reference signals that are
transmitted by a first wireless device using a set of combinations
of analog beamforming parameters for two or more beams that carry
two or more MIMO streams, where the set of reference signals are
transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters. The operations of 2205 may be performed
according to the methods described herein. In some examples,
aspects of the operations of 2205 may be performed by a reference
signal manager as described with reference to FIGS. 12 through
16.
At 2210, the UE or base station may select a first combination of
analog beamforming parameters based on the measured channel quality
of the set of reference signals. The operations of 2210 may be
performed according to the methods described herein. In some
examples, aspects of the operations of 2210 may be performed by a
wideband parameter manager as described with reference to FIGS. 12
through 16.
At 2215, the UE or base station may estimate an effective channel
between the second wireless device and the first wireless device
for each of the different combinations of the one or more sets of
transmit beamforming parameters and the one or more sets of receive
beamforming parameters, and where the first combination of analog
beamforming parameters is selected based on a magnitude of the
effective channel estimates. The operations of 2215 may be
performed according to the methods described herein. In some
examples, aspects of the operations of 2215 may be performed by a
channel estimation component as described with reference to FIGS.
12 through 16.
At 2220, the UE or base station may transmit a second reference
signal to the first wireless device using the first combination of
analog beamforming parameters for determination of a set of
transmission baseband precoder parameters at the first wireless
device. The operations of 2220 may be performed according to the
methods described herein. In some examples, aspects of the
operations of 2220 may be performed by a reference signal manager
as described with reference to FIGS. 12 through 16.
At 2225, the UE or base station may communicate with the first
wireless device via the two or more beams based on the first
combination of analog beamforming parameters. The operations of
2225 may be performed according to the methods described herein. In
some examples, aspects of the operations of 2225 may be performed
by a MIMO manager as described with reference to FIGS. 12 through
16. In some cases, the communicating with the first wireless device
includes data communications via the two or more MIMO streams on
the two or more beams, where the two or more beams use the first
combination of analog beamforming parameters and the set of
transmission baseband precoder parameters. In some cases, the data
communications include a third reference signal for determination
of a set of receive baseband combiner parameters to be applied to
baseband signals of the two or more beams at the second wireless
device.
FIG. 23 shows a flowchart illustrating a method 2300 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The operations
of method 2300 may be implemented by a UE 115 or base station 105
or its components as described herein. For example, the operations
of method 2300 may be performed by a communications manager as
described with reference to FIGS. 12 through 16. In some examples,
a UE or base station may execute a set of instructions to control
the functional elements of the UE or base station to perform the
functions described below. Additionally or alternatively, a UE or
base station may perform aspects of the functions described below
using special-purpose hardware.
At 2305, the UE or base station may measure, at a second wireless
device, a channel quality of a set of reference signals that are
transmitted by a first wireless device using a set of combinations
of analog beamforming parameters for two or more beams that carry
two or more MIMO streams, where the set of reference signals are
transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters. The operations of 2305 may be performed
according to the methods described herein. In some examples,
aspects of the operations of 2305 may be performed by a reference
signal manager as described with reference to FIGS. 12 through
16.
At 2310, the UE or base station may select a first combination of
analog beamforming parameters based on the measured channel quality
of the set of reference signals. The operations of 2310 may be
performed according to the methods described herein. In some
examples, aspects of the operations of 2310 may be performed by a
wideband parameter manager as described with reference to FIGS. 12
through 16.
At 2315, the UE or base station may transmit a report that
indicates the first combination of analog beamforming parameters is
selected for the analog beamforming parameters, and where the
report indicates a codebook index value for a codebook of
beamforming parameters, and where the codebook of beamforming
parameters maps codebook index values to the different combinations
of the one or more sets of transmit beamforming parameters and the
one or more sets of receive beamforming parameters. The operations
of 2315 may be performed according to the methods described herein.
In some examples, aspects of the operations of 2315 may be
performed by a codebook manager as described with reference to
FIGS. 12 through 16.
At 2320, the UE or base station may communicate with the first
wireless device via the two or more beams based on the first
combination of analog beamforming parameters. The operations of
2320 may be performed according to the methods described herein. In
some examples, aspects of the operations of 2320 may be performed
by a MIMO manager as described with reference to FIGS. 12 through
16.
FIG. 24 shows a flowchart illustrating a method 2400 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The operations
of method 2400 may be implemented by a UE 115 or base station 105
or its components as described herein. For example, the operations
of method 2400 may be performed by a communications manager as
described with reference to FIGS. 12 through 16. In some examples,
a UE or base station may execute a set of instructions to control
the functional elements of the UE or base station to perform the
functions described below. Additionally or alternatively, a UE or
base station may perform aspects of the functions described below
using special-purpose hardware.
At 2405, the UE or base station may measure, at a second wireless
device, a channel quality of a set of reference signals that are
transmitted by a first wireless device using a set of combinations
of analog beamforming parameters for two or more beams that carry
two or more MIMO streams, where the set of reference signals are
transmitted for different combinations of one or more sets of
transmit beamforming parameters and one or more sets of receive
beamforming parameters. The operations of 2405 may be performed
according to the methods described herein. In some examples,
aspects of the operations of 2405 may be performed by a reference
signal manager as described with reference to FIGS. 12 through
16.
At 2410, the UE or base station may select a first combination of
analog beamforming parameters based on the measured channel quality
of the set of reference signals. The operations of 2410 may be
performed according to the methods described herein. In some
examples, aspects of the operations of 2410 may be performed by a
wideband parameter manager as described with reference to FIGS. 12
through 16.
At 2415, the UE or base station may transmit an indication to the
first wireless device of a set of transmission baseband precoder
parameters to be applied to baseband signals for transmissions from
the first wireless device using the two or more beams. The
operations of 2415 may be performed according to the methods
described herein. In some examples, aspects of the operations of
2415 may be performed by a precoding parameter manager as described
with reference to FIGS. 12 through 16. In some cases, the
indication to the first wireless device is a precoding matrix
indicator (PMI) that is mapped to a codebook of sets of
transmission baseband precoder parameters.
At 2420, the UE or base station may communicate with the first
wireless device via the two or more beams based on the first
combination of analog beamforming parameters. The operations of
2420 may be performed according to the methods described herein. In
some examples, aspects of the operations of 2420 may be performed
by a MIMO manager as described with reference to FIGS. 12 through
16.
FIG. 25 shows a flowchart illustrating a method 2500 that supports
multi-beam selection for beamformed MIMO wireless communications in
accordance with aspects of the present disclosure. The operations
of method 2500 may be implemented by a UE 115 or base station 105
or its components as described herein. For example, the operations
of method 2500 may be performed by a communications manager as
described with reference to FIGS. 12 through 16. In some examples,
a UE or base station may execute a set of instructions to control
the functional elements of the UE or base station to perform the
functions described below. Additionally or alternatively, a UE or
base station may perform aspects of the functions described below
using special-purpose hardware.
At 2505, the UE or base station may receive, at a first wireless
device, a set of reference signals that are transmitted by a second
wireless device using a set of combinations of analog beamforming
parameters for two or more beams that carry two or more MIMO
streams. The operations of 2505 may be performed according to the
methods described herein. In some examples, aspects of the
operations of 2505 may be performed by a reference signal manager
as described with reference to FIGS. 12 through 16.
At 2510, the UE or base station may determine a set of analog
beamforming parameters for the two or more beams based on
measurements of the set of reference signals. The operations of
2510 may be performed according to the methods described herein. In
some examples, aspects of the operations of 2510 may be performed
by a wideband parameter manager as described with reference to
FIGS. 12 through 16.
At 2515, the UE or base station may determine a set of transmission
baseband precoder parameters to be applied to baseband signals of
the two or more beams based on a channel estimation of a channel
between the first wireless device and the second wireless device.
The operations of 2515 may be performed according to the methods
described herein. In some examples, aspects of the operations of
2515 may be performed by a precoding parameter manager as described
with reference to FIGS. 12 through 16.
At 2520, the UE or base station may determine a set of receive
baseband combiner parameters to be applied to baseband signals of
the two or more beams based on the channel estimation. The
operations of 2520 may be performed according to the methods
described herein. In some examples, aspects of the operations of
2520 may be performed by a combiner parameter manager as described
with reference to FIGS. 12 through 16.
At 2525, the UE or base station may communicate with the second
wireless device using the two or more beams based on the set of
analog beamforming parameters, the set of transmission baseband
precoder parameters, and the set of receive baseband combiner
parameters. The operations of 2525 may be performed according to
the methods described herein. In some examples, aspects of the
operations of 2525 may be performed by a MIMO manager as described
with reference to FIGS. 12 through 16.
It should be noted that the methods described herein describe
possible implementations, and that the operations and the steps may
be rearranged or otherwise modified and that other implementations
are possible. Further, aspects from two or more of the methods may
be combined.
Techniques described herein may be used for various wireless
communications systems such as code division multiple access
(CDMA), time division multiple access (TDMA), frequency division
multiple access (FDMA), orthogonal frequency division multiple
access (OFDMA), single carrier frequency division multiple access
(SC-FDMA), and other systems. A CDMA system may implement a radio
technology such as CDMA2000, Universal Terrestrial Radio Access
(UTRA), etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards.
IS-2000 Releases may be commonly referred to as CDMA2000 1.times.,
1.times., etc. IS-856 (TIA-856) is commonly referred to as CDMA2000
1.times.EV-DO, High Rate Packet Data (HRPD), etc. UTRA includes
Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may
implement a radio technology such as Global System for Mobile
Communications (GSM).
An OFDMA system may implement a radio technology such as Ultra
Mobile Broadband (UMB), Evolved UTRA (E-UTRA), Institute of
Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE
802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are
part of Universal Mobile Telecommunications System (UMTS). LTE,
LTE-A, and LTE-A Pro are releases of UMTS that use E-UTRA. UTRA,
E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR, and GSM are described in
documents from the organization named "3rd Generation Partnership
Project" (3GPP). CDMA2000 and UMB are described in documents from
an organization named "3rd Generation Partnership Project 2"
(3GPP2). The techniques described herein may be used for the
systems and radio technologies mentioned herein as well as other
systems and radio technologies. While aspects of an LTE, LTE-A,
LTE-A Pro, or NR system may be described for purposes of example,
and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of
the description, the techniques described herein are applicable
beyond LTE, LTE-A, LTE-A Pro, or NR applications.
A macro cell generally covers a relatively large geographic area
(e.g., several kilometers in radius) and may allow unrestricted
access by UEs with service subscriptions with the network provider.
A small cell may be associated with a lower-powered base station,
as compared with a macro cell, and a small cell may operate in the
same or different (e.g., licensed, unlicensed, etc.) frequency
bands as macro cells. Small cells may include pico cells, femto
cells, and micro cells according to various examples. A pico cell,
for example, may cover a small geographic area and may allow
unrestricted access by UEs with service subscriptions with the
network provider. A femto cell may also cover a small geographic
area (e.g., a home) and may provide restricted access by UEs having
an association with the femto cell (e.g., UEs in a closed
subscriber group (CSG), UEs for users in the home, and the like).
An eNB for a macro cell may be referred to as a macro eNB. An eNB
for a small cell may be referred to as a small cell eNB, a pico
eNB, a femto eNB, or a home eNB. An eNB may support one or multiple
(e.g., two, three, four, and the like) cells, and may also support
communications using one or multiple component carriers.
The wireless communications systems described herein may support
synchronous or asynchronous operation. For synchronous operation,
the base stations may have similar frame timing, and transmissions
from different base stations may be approximately aligned in time.
For asynchronous operation, the base stations may have different
frame timing, and transmissions from different base stations may
not be aligned in time. The techniques described herein may be used
for either synchronous or asynchronous operations.
Information and signals described herein may be represented using
any of a variety of different technologies and techniques. For
example, data, instructions, commands, information, signals, bits,
symbols, and chips that may be referenced throughout the
description may be represented by voltages, currents,
electromagnetic waves, magnetic fields or particles, optical fields
or particles, or any combination thereof.
The various illustrative blocks and modules described in connection
with the disclosure herein may be implemented or performed with a
general-purpose processor, a DSP, an ASIC, an FPGA, or other
programmable logic device, discrete gate or transistor logic,
discrete hardware components, or any combination thereof designed
to perform the functions described herein. A general-purpose
processor may be a microprocessor, but in the alternative, the
processor may be any conventional processor, controller,
microcontroller, or state machine. A processor may also be
implemented as a combination of computing devices (e.g., a
combination of a DSP and a microprocessor, multiple
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration).
The functions described herein may be implemented in hardware,
software executed by a processor, firmware, or any combination
thereof. If implemented in software executed by a processor, the
functions may be stored on or transmitted over as one or more
instructions or code on a computer-readable medium. Other examples
and implementations are within the scope of the disclosure and
appended claims. For example, due to the nature of software,
functions described herein can be implemented using software
executed by a processor, hardware, firmware, hardwiring, or
combinations of any of these. Features implementing functions may
also be physically located at various positions, including being
distributed such that portions of functions are implemented at
different physical locations.
Computer-readable media includes both non-transitory computer
storage media and communication media including any medium that
facilitates transfer of a computer program from one place to
another. A non-transitory storage medium may be any available
medium that can be accessed by a general purpose or special purpose
computer. By way of example, and not limitation, non-transitory
computer-readable media may include random-access memory (RAM),
read-only memory (ROM), electrically erasable programmable ROM
(EEPROM), flash memory, compact disk (CD) ROM or other optical disk
storage, magnetic disk storage or other magnetic storage devices,
or any other non-transitory medium that can be used to carry or
store desired program code means in the form of instructions or
data structures and that can be accessed by a general-purpose or
special-purpose computer, or a general-purpose or special-purpose
processor. Also, any connection is properly termed a
computer-readable medium. For example, if the software is
transmitted from a website, server, or other remote source using a
coaxial cable, fiber optic cable, twisted pair, digital subscriber
line (DSL), or wireless technologies such as infrared, radio, and
microwave, then the coaxial cable, fiber optic cable, twisted pair,
DSL, or wireless technologies such as infrared, radio, and
microwave are included in the definition of medium. Disk and disc,
as used herein, include CD, laser disc, optical disc, digital
versatile disc (DVD), floppy disk and Blu-ray disc where disks
usually reproduce data magnetically, while discs reproduce data
optically with lasers. Combinations of the above are also included
within the scope of computer-readable media.
As used herein, including in the claims, "or" as used in a list of
items (e.g., a list of items prefaced by a phrase such as "at least
one of" or "one or more of") indicates an inclusive list such that,
for example, a list of at least one of A, B, or C means A or B or C
or AB or AC or BC or ABC (i.e., A and B and C). Also, as used
herein, the phrase "based on" shall not be construed as a reference
to a closed set of conditions. For example, an exemplary step that
is described as "based on condition A" may be based on both a
condition A and a condition B without departing from the scope of
the present disclosure. In other words, as used herein, the phrase
"based on" shall be construed in the same manner as the phrase
"based at least in part on."
In the appended figures, similar components or features may have
the same reference label. Further, various components of the same
type may be distinguished by following the reference label by a
dash and a second label that distinguishes among the similar
components. If just the first reference label is used in the
specification, the description is applicable to any one of the
similar components having the same first reference label
irrespective of the second reference label, or other subsequent
reference label.
The description set forth herein, in connection with the appended
drawings, describes example configurations and does not represent
all the examples that may be implemented or that are within the
scope of the claims. The term "exemplary" used herein means
"serving as an example, instance, or illustration," and not
"preferred" or "advantageous over other examples." The detailed
description includes specific details for the purpose of providing
an understanding of the described techniques. These techniques,
however, may be practiced without these specific details. In some
instances, well-known structures and devices are shown in block
diagram form in order to avoid obscuring the concepts of the
described examples.
The description herein is provided to enable a person skilled in
the art to make or use the disclosure. Various modifications to the
disclosure will be readily apparent to those skilled in the art,
and the generic principles defined herein may be applied to other
variations without departing from the scope of the disclosure.
Thus, the disclosure is not limited to the examples and designs
described herein, but is to be accorded the broadest scope
consistent with the principles and novel features disclosed
herein.
* * * * *